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BRITL    53  1.T42    c.  1 

THURSTON    #    ANIMAL    AS    MACHINE    AND 

PRIME    MOTOR    AND    LAWS    OF    ENERGETIC 


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The  Publishers  and  the  Author  will  be  grateful  to 
any  of  the  readers  of  this  volume  who  will  kiudly  call 
their  attention  to  any  errors  of  omission  or  of  commission 
that  they  may  find  therein.  It  is  intended  to  make 
our  publications  standard  works  of  study  and  reference, 
and,  to  that  end,  the  greatest  accuracy  is  sought.  It 
rarely  happens  that  the  early  editions  of  works  of  any 
size  are  free  from  errors  ;  but  it  is  the  endeavor  of  the 
Pubhshers  to  see  them  removed  immediately  upon  being 
discovered,  and  it  is  therefore  desired  that  the  Author 
may  be  aided  in  his  task  of  revision,  from  time  to  time, 
by  the  kindly  criticism  of  his  readers. 

JOHN    WILEY  &   SONS. 
53  East  Tenth  Street. 


I 


I 


THE    ANIMAL  ^  ^^ 


AS  A 


MACHINE  AND  A  PRIME  MOTOR, 

AND  THE  LAWS  OF  ENERGETICS. 


R.  H.  THURSTON, 


FIRST    EDITION, 
FIRST    THOUSAND. 


NEW   YORK: 

JOHN    WILEY    &    SONS, 

53  East  Tenth  Street. 
1894. 


Copyright,  1894, 

BY 

R.  H.  THURSTON. 


CONTENTS. 


I.    INTRODUCTION. 

^''^-  PAGE 

1.  Energy  and  its  Transformation i 

2.  Forces  and  their  Classification n 

3.  Energy  defined - 

4.  Mechanics  defined 3 

5.  Energetics  defined g 

6.  Relations  of  Matter,  Force,  and  Energy  .         .         .         .10 

7.  Laws  of  Energetics 24 

8.  Newton's  Laws 26 

9.  Algebraic  Expression  of  Energy-changes        .         .         .         .27 

10.  The  Object  of  all  Mechanism 30 

11.  The  Sources  and  Kinds  of  Energy 31 

12.  Forms  of  Motor .         ,         ,  3^ 

II.    THE   ANIMAL   AS   A    PRIME   MOTOR. 

13.  The  Animal  as  a  Machine 37 

14.  The  Animal  as  a  Motor  ........  38 

15.  The  Processes  of  Vital  Machines 45 

16.  The  Efficiency  of  the  Animal  System 50 

17.  The  Work  of  the  Animal  Machine 50 

18.  Work  of  Men  and  Animals 53 

19.  Effective  Methods  of  Application  of  Power     .         .         .         .59 

20.  Draught  of  Vehicles          ••......  61 

21.  Intensity  of  Muscular  Efifort 58 

22.  The  Uses  of  Food ^q 

23.  Dietaries           •••••••...  73 

24.  Mechanism  of  Transmission  of  Force 78 

iii 


IV  CONTENTS. 

ART.  PAGE 

25.  Equation  of  Applied  Animal  Power 79 

26.  Selection  and  Care  of  Men  and  Animals        .         .         .         .80 


III.    FINAL   DEDUCTIONS. 

27.  Progress  of  Improvement 84 

28.  Objects  of  Search    ......  .         .     86 

29.  The  Living  Body  as  a  Machine 89 

30.  Methods  of  Production  of  Animal  Energy       .  .         .         .92 

31.  Advantages  of  Substitution  of  Nature's  Methods    .         .         -94 

32.  Costs 97 


THE  ANIMAL 

AS   A 

MACHINE  AND   A   PRIME  MOTOR 


INTRODUCTION. 

ENERGY  AND  ITS  TRANSFORMATIONS. 

ENERGETICS  AND   ITS   LAWS. 

I.  Energy  and  its  Transformations  are  the  source 
and  the  method  of  all  useful  work,  as  of  all  natural 
phenomena  involving  motions  of  masses  or  of  mole- 
cules of  whatever  kind.  All  ''  prime  movers  "  are  ma- 
chines by  means  of  which  man  diverts  energy  from 
natural  channels  and  compels  it  to  do  his  own  work. 
The  water-wheels  and  windmills  simply  transfer  the 
energy  of  the  moving  fluid  to  the  machinery  of  the 
transmission  through  which  it  performs  useful  work  ; 
the  heat-engines  and  electric  machinery  transfer  energy, 
and  at  the  same  time  convert  it  from  the  thermal  or  the 
electrical  to  the  dynamic  form  for  application,  and 
thermodynamic  or  electro-dynamic  apparatus  thus  have 
two  distinct  functions. 

In  some  instances  we  may  observe  a  succession  of 


2  THE  ANIMAL   AS  A   MACHINE. 

transformations  of  energy,  as  where  a  steam  boiler 
transforms,  and  stores  for  transmission  to  the  engine, 
energy  of  chemical  afifinity ;  the  engine,  in  turn,  trans- 
forming it  into  mechanical  energy  and  transmitting  it 
to  a  dynamo-electric  machine,  where  it  is  again  trans- 
formed, changing  into  the  electrical  current,  to  be  sent 
perhaps  miles  away  to  an  electro-dynamic  machine  or 
motor,  where  its  retransformation  into  mechanical 
power  occurs,  and  it  is  set  at  the  work  of  driving  a  mill 
or  other  collection  of  mechanisms.  A  telephone  sys- 
tem illustrates  in  another  way  similar  transformations 
and  retransformations  of  mechanical  and  electric  energy, 
and  Mr.  Hammer  has  thus  produced  a  system  involving 
many  transformations  and  including  a  circuit  of  a  hun- 
dred miles. 

Nature  herself  has  in  these  cases  usually  already  per- 
formed some  such  transformations  of  energy  in  the 
reduction  of  that  so  collected  and  applied  to  the  form 
in  which  the  mechanic  and  the  engineer  finds  it  ready 
to  his  hand.  The  water  has  been  raised  from  the  lakes 
and  the  sea,  and  distributed  by  the  clouds  to  the  elevated 
sources  from  which  it  flows  downward  in  the  streams ; 
the  winds  are  the  result  of  differences  of  temperature 
and  the  action  of  heat  energy ;  the  heat  of  combustion 
is  the  representative  of  an  earlier  form  of  energy  in 
which  the  heat  of  the  sun  and  of  the  still  cooling  earth, 
and  the  formation  of  the  coal  deposits  in  early  geo- 
logical periods,  played  a  part.  In  a  general  way  it  has 
come  to  be  seen  that  every  display  of  energy,  like  every 
new  form  of  matter,  is  the  result  of  change  in  some 
antecedent  form,  and  that  neither  matter  nor  energy 
can  be  destroyed.  This  has  been  admitted  from  the 
time  of  Lavoisier,  so  far  as  it  affects  matter ;  it  has 


ENERGY  AND  ITS    TRANSFORMATIONS.  3 

been  admitted  as  applicable  to  physical  energy  since 
the  doctrines  of  the  correlation  of  forces  and  the  per- 
sistence of  energy  became  accepted  by  men  of  science  ; 
and  we  are  gradually  progressing  towards  the  establish- 
ment of  a  law  of  persistence  of  all  existence,  whether 
of  matter,  of  force  and  energy,  or  of  organic  vitality, 
and  perhaps  even  to  its  extension  until  it  includes  in- 
tellectual and  soul  life. 

We  see  that  in  the  beginning  there  entered  upon 
an  existence  of  indefinite  duration  a  great  universe 
of  matter  endowed  with  its  characterizing  attributes 
— the  forces.  These  forces,  acting  upon  a  definite 
quantity  of  matter  with  definite  intensity,  give  origin 
to  a  fixed  amount  of  actual  energy,  and  become  capa- 
ble of  producing  another  fixed  quantity  of  what  is  now 
potential  energy.  Energy  thus  brought  into  exist- 
ence remains  constant  in  total  amount  as  the  quantity 
of  created  matter  remains  constant. 

The  action  of  these  forces  upon  this  matter  has  given 
rise  to  every  phenomenon  which  has  come,  or  which 
can  come,  within  the  range  of  scientific  inquiry. 

2.  Forces  are  Classified,  according  to  their  methods 
of  affecting  matter,  into  three  great  classes  : 

(i)  Those  forces  with  which  we  are  able  to  make 
ourselves  so  readily  and  thoroughly  familiar  that  we  find 
no  difficulty  in  assigning  to  each  of  them  its  proper 
place  in  the  scheme  of  scientific  systematization,  and 
which  we  have  found  it  comparatively  easy  to  distin- 
guish by  their  peculiar  and  readily  observed  effects. 
These  include  the  familiar  physical  forces,  as  gravita- 
tion, electrical,  chemical,  and  mechanical  forces. 

(2)  The  vital  forces — those  which  are  preservative  of 
all  life,  which  produce   and  promote  the  growth  of  or- 


4  THE  ANIMAL  AS  A   MACHINE. 

ganisms  having  life,  and  which  are  less  easily  under- 
stood, more  difficult  to  study,  and  far  less  subject  to 
the  modifying  power  of  human  action,  than  are  those 
of  the  first  described  class. 

(3)  The  forces  of  the  soul  and  of  the  intellect — 
those  most  wonderful  and  most  mysterious  of  all  known 
forms  of  force — forces  of  the  nature  of  which  we  know 
nothing,  and  of  the  effects  of  which,  actual  and  possible, 
we  have  the  least  comprehension. 

By  the  study  of  the  universe  as  it  now  exists,  philos- 
ophers are  led  to  perceive  that  its  present  state  is  such 
as  would  have  resulted  had  the  various  forms  of  matter 
with  which  we  are  surrounded,  and  of  which  we  our- 
selves are  corporeally  formed,  and  had  other  existences 
which  we  suppose  to  form  a  part  of  our  universe  been, 
at  the  beginning,  so  distributed  and  so  placed  in  refer- 
ence to  the  several  kinds  of  forces  that  the  former, 
acted  freely  upon  by  the  latter,  should,  by  a  continuity 
of  never-ceasing,  ever-progressing  change,  take  those  in- 
finite variations  of  growth,  and  all  that  inconceivable 
variety  of  shapes,  that  have  supposed  to  have  been,  by 
the  process  called  ''  evolution,"  brought  into  the  visible 
universe.* 

Studying  the  accessible  universe,  as  far  as  we  are  per- 
mitted, in  greater  detail,  we  find  that  each  of  the  var- 
ious kinds  of  forces  set  at  work  to  modify  the  position 
and  character  of  matter  has  a  special  part  to  play,  a 
peculiar  work  to  do  ;  we  find  that  the  first  class  has  a 

*As  early  as  1854  Helmholtz  showed  that  the  condensation  of  an 
infinitely  diffused  nebulous  mass  of  matter,  to  form  the  stellar  systems 
of  the  universe,  by  gravitation,  was  sufficient  to  furnish  all  existing 
heat-energy,  and  a  source  of  all  that  mechanical  and  other  transformed 
energy  known  now  to  exist. 


ENERGY  AND  ITS    TRANSFORMATIONS.  5 

sphere  of  operation  which  is  fully  within  the  reach  of 
our  senses;  that  the  second  class  of  forces  is  also,  to  a 
certain  extent,  familiar  to  us  through  a  knowledge  of 
their  effects:  but  the  last  of  these  several  classes  of 
forces  existing  in  nature  is,  as  yet,  quite  beyond  our 
ken. 

Studying  these  forms  of  manifestation  of  force  which 
are  divided  between  the  first  two  classes,  we  perceive  a 
distinction  which  is  as  well  defined  as  is  the  line  sepa- 
rating the  two  classes  of  phenomena  to  which  they  give 
rise. 

(i)  T\iQ  physical  forces — and  it  is  intended  here  to  in- 
clude the  mechanical  and  chemical,  as  well  as  the  forces 
which  are  usually  alone  treated  of  in  works  on  physics — 
are  capable  of  being  observed,  of  being  distinguished 
by  certain  readily  defined  qualities,  and  of  being  ac- 
curately measured  quantitatively.  The  conditions  which 
lead  to  their  active  display  are  capable  of  being  ex- 
actly ascertained,  and  the  precise  results  of  their  opera- 
tions under  any  given  set  of  conditions  may  usually  be 
accurately  predicted.  These  conditions  are  subject  to 
certain  definite  modifications  by  the  power  of  man, 
and  the  changes  of  effect  which  will  result  from  such 
changes  of  condition  may  be  predicted.  The  effects 
which  nature  produces  in  certain  cases  by  the  action  of 
these  forces  may  be  modified  by  man  without  entirely 
defeating  the  original  tendency  to  bring  about  a  certain 
change  of  mode  of  action  of  existing  energy.  These 
forces,  acting  alone,  never  give  rise  to  the  more  intri- 
cate forms  seen  in  nature.  Their  highest  product  in 
the  whole  morphological  range  is  a  crystal  of  more  or 
less  perfect  shape,  but  of  a  form  which  is  always  of 
some  simple  geometrical  class.     These  forces  do  not 


6  THE  ANIMAL   AS  A   MACHINE. 

exhibit  the  play  of  definitely  directed  energy  tending 
to  effect  a  perfectly  well  defined,  though  remote,  re- 
sult. Their  effects  are  the  accidental  and  the  inci- 
dental, so  far  as  the  more  wonderful  and  most  intricate 
of  the  operations  of  nature  are  concerned. 

(2)  The  vital  forces,  on  the  other  hand,  effect  opera- 
tions which  human  power  can  only  touch  to  impede  or 
to  destroy.  They  have  for  their  mission  the  creation  of 
strangely  complicated  and  curiously  organized  struc- 
tures, in  ivhich  are  stored  certain  definite  amounts  of 
energy,  and  which  are  given  a  power  of  acquiring  and 
of  applying  extraneous  energy,  in  probably  also  defi- 
nite amount,  to  the  accomplishment  of  certain  tasks. 
Man  may  modify  their  operation  and  may  produce 
some  change  in  the  phenomena  which  they  are  ap- 
pointed to  bring  about  ;  but  it  is  only  by  deranging 
their  action.  He  can  mar  their  work,  but  cannot  di- 
rectly aid  them.  That  store  of  vital  energy  which  was 
created  in  the  infinite  past,  and  which  is  now  passing 
through  one  after  another  of  the  forms  of  life,  new  and 
old,  which  are  constantly  coming  into  the  field  of  our 
cognizance,  and  as  constantly  disappearing  from  view, 
is  continually  developing  organisms  of  every  grade  from 
the  simple  life-seed,  if  such  exist — from  the  basic  pro- 
toplasm— to  the  human  ruler  of  them  all. 

Of  these  two  sets  of  forces,  the  one  is  blind  and  aim- 
less, unintelligent  as  to  the  direction  of  its  efforts,  in- 
different as  to  its  results,  and  is  governed  by  laws 
which,  under  all  known  conditions,  are  as  simple  as 
they  are  invariable.  The  other  set  appears  to  act  at 
all  times  upon  a  definite,  far-reaching  plan,  and  these 
forces  set  themselves  intelligently  about  the  production 
of  the  most  elegant  and  intricate  of  designs,  and  the 


ENERGY  AND  ITS   TRANSFORMATIONS.  7 

elaboration  of  the  most  wonderful  and  mysterious  of 
organisms.  It  is  only  in  the  structures  which  are  their 
work  that  the  strange,  the  incomprehensible  phenom- 
ena of  life  are  exhibited  to  the  intelligence  which 
vainly  endeavors  to  understand  them."^ 

3.  Energy,  "living  Force,"  ever-living  force,  as  we 
are  now  learning  to  regard  it ;  vis  viva,  as  its  first 
discoverer,  Leibnitz,  called  it ;  the  force  illustrated  in 
all  life  and  motion,  as  we  now  know  it ;  energy,  as  Dr. 
Young  first  denominated  it :  all  these  expressions  for 
one  common  quality  of  every  body,  substance,  or 
system,  in  motion  either  as  to  its  atoms  or  molecules 
or  as  to  its  mass,  denote  that  mysterious  property 
by  which  all  growth,  all  life,  all  changes  in  physical 
things  or  physical  substance  are  brought  about  and 
continued.  The  work  of  the  vegetable  kingdom,  in 
the  elevation  of  the  simpler,  inorganic  compositions 
found  in  nature  to  the  higher,  complex,  organic  forms 
in  which  they  find  their  culmination  ;  those  of  the  ani- 
mal system  which  take  these  complex  forms  and  erect 
them  in  a  still  more  complicated  animal  structure  and 
supply  it  with  the  powers  of  animal  life  ;  the  work  of 
the  living  creature  in  again  reducing  these  complicated 
structures  to  the  lower  and  simplest  forms,  availing  it- 
self of  their  latent  energy  in  the  production  of  all  the 
grandest  results  of  physical  and  intellectual  life :  all 
these  are  but  manifestations  in  various  ways  of  the 
ever-living  forces,  the  never-ceasing  energies,  of  the 
universe. 

In  its  two  forms,  kinetic  and  potential,  actual  and 

*The  preceding  matter  is  from  the  vice-president's  address  before 
the  American  Association  for  the  Advancement  of  Science,  R.  H. 
Thurston,  1878. 


8  THE  ANIMAL  AS  A   MACHINE. 

latent,  the  sum  of  which  is  constant  throughout  the 
universe,  energy  is  the  source  and  the  basis  of  all  life, 
of  all  motion,  of  all  development,  of  all  evolution.  It 
is  the  mainspring  of  all  physical  phenomena ;  and  the 
science  of  Energetics  is  the  foundation  of  chemistry, 
as  of  physics  ;  of  astronomy,  as  of  the  mechanics  of  en- 
gineering. Whatever  we  know  of  matter,  even,  is  dis- 
covered to  us  by  these  methods  of  display  of  energy  in 
connection  with  it. 

The  science  of  energetics  itself  is  one  division  of  a 
broader  science,  that  of  Mechanics, — that  great  science 
which  bears  more  or  less  directly  upon  every  phenom- 
enon of  nature  and  the  universe,  and  which  is  at  the 
foundation  of  all  the  applied  sciences,  of  all  the  arts  of 
construction,  of  all  the  exact  sciences  of  physics  and 
chemistry,  of  astronomy,  and  of  forces  and  motions. 

4.  Mechanics  thus  includes  four  principal  divisions  :* 
(i)  Statics  treats  of  the  relations  of  forces  acting  in 

any  system  when  no  motion  results  from  that  action. 

(2)  Kinematics  treats  of  the  relations  of  motions  sim- 
ply, of  their  composition  and  resolution,  and  of  their 
resultant  effects. 

(3)  Dynamics  or  Ki7ietics  treats  of  the  motions  pro- 
duced in  ponderable  bodies  by  the  action  of  forces. 

(4)  Energetics  treats  of  the  measurement,  the  trans- 
fer, and  the  transformations  of  energy  under  the  action 
of  forces,  and  of  their  result  in  the  variation  of  the 
method  of  its  manifestation. 

5.  Energetics  is  defined,  therefore,  as  that  science 
which  treats  of  all  natural  phenomena  which,  through 


*  Several  pages  are  here  taken  mainly  from  "The    Manual  of  the 
Steam   Engine,"  vol.  i,  by  R.  H.  Thurston  ;   N.  Y.,  J.  Wiley  &  Sons. 


ENERGY  AND  ITS   TRANSFORMATIONS.  g 

the  action  of  force  upon  matter,  result  in  the  produc- 
tion of  motion  ;  whether  it  be  a  relative  motion  of 
atoms,  of  molecules,  or  of  masses.  It  is  that  science 
"  whose  subjects  are  material  bodies  and  physical  phe- 
nomena." *     We  may  here  repeat : 

Energetics  thus  treats  of  modifications  of  energy 
under  the  action  of  forces,  and  of  its  transformation 
from  one  mode  of  manifestation  to  another,  and  from 
one  body  to  another ;  and  within  this  broader  science 
is  comprehended  that  latest  of  the  minor  sciences — of 
which  the  heat-engines  and  especially  the  steam-engine 
illustrate  the  most  important  applications — Thermo- 
dynamics, The  science  of  energetics  is  simply  a  wider 
generalization  of  principles  which  have  been  established 
one  at  a  time,  and  by  philosophers  widely  separated, 
both  geographically  and  historically,  by  both  space 
and  time,  and  which  have  been  slowly  aggregated,  to 
form  one  after  another  of  the  physical  sciences,  and 
out  of  which  we  are  slowly  evolving  wider  generaliza- 
tions ;  thus  tending  toward  a  condition  of  scientific 
knowledge  which  renders  more  and  more  probable  the 
truth  of  a  principle,  still  broader  than  this  science, 
even,  and  which  was  enunciated  before  Science  had  a 
birthplace  or  a  name  ;  i.e.  : 

All  that  exists,  whether  matter  or  force,  and  in  zv hat- 
ever  form,  is  indestructible  by  any  finite  poiuer. 

As  already  remarked,  that  matter  is  indestructible 
by  finite  power  became  admitted  as  soon  as  the  chem- 
ists, led  by  Lavoisier,  began  to  apply  the  balance,  and 
jwere  thus  able  to  show  that  in  all  chemical  change  there 
occurs  only  a  modification  of  form  or  of  combination 

*  Rankine  ;  Proc,  Phil.  Soc.  Glasgow  ;  vol.  iii.  No.  6. 


10  THE  ANIMAL  AS  A   MACHINE. 

of  elements,  and  no  loss  of  matter  ever  takes  place. 
The  "  persistence  "  of  energy  was  a  later  discovery,  con- 
sequent largely  upon  the  experimental  determination  of 
the  convertibility  of  heat-energy  into  other  forms  and 
into  mechanical  work,  for  which  we  are  indebted  to 
Rumford  and  Davy,  and  to  the  determination  of  the 
quantivalence  anticipated  by  Newton,  shown  and  com- 
puted approximately  by  Colding  and  Mayer,  measured 
with  great  accuracy  by  Joule  and  Rowland. 

It  is  now  generally  understood  that  all  forms 
of  energy  are  mutually  convertible  with  a  definite 
quantivalence  ;  and  it  is  not  certain  that  even  vital 
and  mental  energy  do  not  fall  within  the  same  cate- 
gory. 

The  essentially  important,  as  well  as  interesting,  fact, 
in  this  connection,  to  the  engineer  as  well  as  to  the 
physicist,  it  should  be  noted,  is  that  the  laws  of  ener- 
getics apply  unqualifiedly  to  atomic  and  molecular 
phenomena,  as  well  as  to  energies  of  masses,  and  to  all 
transformations  of  energy  in  either  class  and  of  any 
kind.  There  is,  dynamically,  absolutely  no  distinction, 
in  this  respect,  between  the  methods  and  processes  of 
chemistry,  of  physics,  and  of  the  mechanics  of  masses. 
All  illustrate  phases  of  one  science,  and  all  are  ener- 
gies of  matter  in  motion. 

6.  Matter,  Force,  and  Energy  are  the  only  quan- 
tities known  to  the  departments  of  natural  science. 
The  science  of  CJiemistry  deals  with  the  forms  which 
matter  assumes  under  the  action  of  measurable  atomic 
molecular  forces  affecting  dissimilar  kinds  of  matter ; 
Physics  is  that  science  which  deals  with  all  the  other 
forms  of  sensible  force  and  their  effects.  The  science 
of  Energetics  treats  of  the  action   of  forces  producing 


ENERGY  AND  ITS   TRANSFORMATIONS.  II 

or  modifying  energy,  whatever  the  kind  of  force,  what- 
ever the  kind  of  matter :  it  thus  covers  the  whole 
range  of  chemistry  and  physics. 

Matter  is  that  which  is  capable  of  directly  affecting 
the  senses,  and  which  occupies  space.  Nothing  is 
known  of  the  ultimate  nature  of  matter,  and  we  are 
acquainted  with  it  only  as  it  affects  the  organs  of  the 
body.  It  is  usually  divided  into  four  classes  :  solids, 
liquids,  gases,  and  imponderable  matter ;  the  latter 
meaning  that  which  cannot  be  assigned  a  finite  specific 
measure  of  mass  or  weight.  The  luminiferous  ether  is 
an  example  of  this  last ;  the  other  three  are  familiar 
forms. 

A  Body  is  a  limited  portion  of  matter. 

Force  is  that  which  produces,  or  tends  to  produce, 
motion,  or  change  of  motion,  in  bodies ;  it  is  measured 
statically  by  the  weight  which  will  counterpoise  it  or 
by  comparison  with  a  known  standard  of  force,  and 
dynamically  by  the  velocity  which  it  will  give  a  known 
freely  moving  mass  in  a  stated  time,  i.e.,  by  the  "ac- 
celeration "  which  it  is  capable  of  producing. 

Work  is  always  performed  by  the  expenditure  of 
energy,  and  is  the  product  of  the  resistance  overcome 
by  a  force,  or  of  the  effort  exerted  by  it,  into  the  space 
through  which  that  action  takes  place.  That  resistance 
may  be  constant,  or  variable,  and  due  to  an  active,  oppos- 
ing force,  to  resisting  pressure,  to  the  inertia  of  masses, 
or  of  molecules  compelled  to  submit  to  acceleration  or 
retardation  ;  or  it  may  be  due  to  any  one  of  the  phys- 
ical or  chemical  forces.  Thus,  if  U  represents  the  work 
done  by  a  force,  F,  acting  through  a  space,  s, 

[/=Fs  =  Rs; (i) 


12  THE  ANIMAL  AS  A   MACHINE, 

and  for  motion  variable  only, 

dU=Fds (2) 

For  variable  forces, 

dU  =  sdF. (3) 

For  forces  and  motion  variable, 

dU=d{Fs) (4) 

The  Unit  of  Work  is  the  product  of  the  units  of  its 
factors  force  and  space,  as  the  foot-pound,  the  kilo- 
grammetre,  the  foot-ton,  the  gramme-centimetre. 

Useful  Work  is  that  which  is  applied  to  the  produc- 
tion of  a  specified  useful  effect ;  Lost  Work  is  that 
which  is  incidentally  wasted,  in  the  endeavor  to  per- 
form useful  work,  in  overcoming  prejudicial  resistances, 
and  in  doing  useless  work  ;  this  waste  occurs  usually 
and  principally  in  overcoming  friction  of  moving 
parts. 

Work  of  Acceleration  is  work  expended  in  producing 
increased  velocity  in  a  freely  moving  body.  The  effort 
exerted,  and  the  resistance  met,  is  dependent  upon  the 
inertia  of  the  mass,  and  is  measured  thus :  A  body 
moving  freely  under  the  action  of  gravity,  i.  e.,  of  a 
force  equal  to  its  own  weight,  acquires,  in  this  latitude, 
a  velocity  of  32.2  feet  (9.81  metres),  nearly,  in  one 
second,  and  the  acceleration,  or  retardation,  of  any 
freely-moving  body  is  proportional  to  the  effort  applied, 
as  to  the  resistance  met  by  it.  If  /is  the  actual  accel- 
eration, if  g  measures  that  produced  by  gravity,  if  F  is 


ENERGY  AND  ITS   TRANSFORM  A  l^IONS.  1 3 

the  statical  measure  of  the  effort,  and  PFis  the  weight 
of  the  body,  we  have 

F'.VVv.f'.g:     t:i::v,-v,:f; 

g 

-'^^^= (5) 

v^  and  7',  being  the  initial  and  final  velocities,  and  t  the 
time  of  action  of  the  accelerating  force. 


fc> 


For  variable  acceleration, 


/=S^ <^) 

^=f-f « 


V    +  V 

The  space,  s,  is  equal  to  "^""^  A  and  the  work  done 
is,  for  uniform  acceleration, 

t  2  g 


W^ ^ (8) 


For  variable  acceleration, 


7/'  vdv 

[/^d{Fs)==:  lV.d.—  =  W  — .     .     .     (9) 


14  THE  ANIMAL  AS  A   MACHINE. 

Since  -^-  =  //,  the  height  due  the  velocity  v,  the  work 

is  equal  to  that  required  to  raise  the  body  through  the 
difference  of  the  two  heights  due  the  initial  and  the 
final  velocities,  respectively. 

Where  the  motion  of  the  machine  or  of  the  part 
doing  work  is  circular,  the  space  traversed  may  be 
measured  by  the  angular  motion  a,  multiplied  by  the 
lever-arm,  /,  and  their  product,  multiplied  by  the  force, 
R^  exerted,  gives  the  measure  of  the  work  done.     Thus  : 

in  which  last  expression  ;/  is  the  number  of  revolutions 
made  in  the  unit  of  time. 

These  values  are  equivalent  to  the  product  of  the 
angular  motion  into  the  moment  of  the  resistance. 

Work  may  also  be  measured,  as  in  steam,  air,  gas,  or 
water  pressure  engines,  by  the  product  of  the  area  of 
piston,  A^  the  mean  intensity  of  pressure  upon  it, /,  the 
length  of  stroke  of  piston,  /,  and  the  number  of  strokes 
made.     Thus, 

U  =  Aphi 
=  Aps 
=  PV, (II) 

when  V  is  the  volume  of  the  working  cylinder  multiplied 
by  the  number  of  strokes ;  in  other  words,  the  volume 
traversed  by  the  piston. 

Where  the  force  acting,  or  the  resistance,  acts  ob- 
liquely to  the  path  traversed,  it  is  evident  that  only  the 
component  in  that  path  is  to  be  considered. 

Diagrams  exhibiting  the  amount  of  work  done  and 


ENERGY  AND  ITS    TRANSFORMATIONS.  1 5 

the  method  of  its  variation  are  often  found  useful.  In 
such  diagrams  the  ordinate  is  usually  made  propor- 
tional to  the  force  acting,  or  to  the  resistance,  while  the 
abscissas  are  made  to  measure  the  space  traversed. 
The  curve  then  exhibits  the  relations  of  these  two 
quantities,  and  the  enclosed  area  is  a  measure  of  the 
work  performed.  With  a  constant  resistance,  the  figure 
is  rectilinear  and  a  parallelogram  ;  with  variable  veloci- 
ties and  resistances,  it  has  a  form  characteristic  of  the 
methods  of  operation  of  the  part  or  of  the  machine 
the  action  of  which  it  illustrates. 

Power  is  defined  as  the  rate  of  work^  and  is  meas- 
ured by  the  quantity  of  work  performed  in  the  unit 
of  time,  as  in  foot-pounds  or  in  kilogrammetres,  per 
minute  or  per  second.  The  unit  commonly  employed 
by  engineers  is  the  "horse-power,"  which  was  defined 
by  Watt  as  33,000  foot-pounds  per  minute,  equivalent 
to  550  per  second,  or  1,980,000  foot-pounds  per  hour. 
This  is  considered  to  be  very  nearly  the  amount  of 
work  performed  by  the  very  heavy  draught-horses  of 
Great  Britain  ;  but  it  considerably  exceeds  the  power 
of  the  average  dray-horse  of  that  and  other  countries, 
for  which  25,000  foot-pounds  may  be  taken  as  a  good 
average  amount. 

The  metric  horse-power,  called  by  the  French  the 
cheval-vapair,  or  force  de  cJieval,  is  about  ij  per  cent, 
less  than  the  British,  being  542.47  foot-pounds  or  75  kilo- 
grammetres per  second,  4500  kilogrammetres  per 
minute,  or  270,000  per  hour.  These  quantities  are  al- 
most invariably  employed  to  measure  the  power  ex- 
pended and  work  done  by  machines." 

*  Various  nations  have  a  standard  "horse-power"  derived  from 
Watt's,  but,  owing  to  differences  in  weights  and  measures,  they  are  not 


i6 


THE  ANIMAL  AS  A    MACHINE. 


It  is  evident  that  power  is  also  measured  by  the  pro- 
duct of  the  resistance,  or  of  the  effort  exerted  into  the 
velocity  of  the  motion  with  which  that  resistance  is 
overcome  or  that  force  exerted.     Since  s  =  vt^ 

U=Rs=  Rvt ; 

and  when  t  becomes  unity,  the  measure  of  the  power, 
or  of  the  equivalent  work  done  in  the  unit  of  time,  is 

U  =  Rv, 

in  which  the  terms  are  given  in  units  of  force  and  space 
as  above. 

The  power  of  a  prime  mover  is  usually  ascertained 
by  experimentally  determining  the  work  done  in  a  given 
time,  the  trial  usually  extending  over  some  hours,  and 
often  several  days.     It  is  measured  in  foot-pounds  or 

identical  ;  but  the  differences  are  usually  less  than  i\  per  cent.  The  fol- 
lowing table,  compiled  by  Mr.  Babcock,  gives  these  standards  in  kilo- 
grammetres  per  second,  and  in  foot-pounds  per  second  expressed  in 
the  foot  and  pound  standards  of  each  country. 

STANDARD  HORSE-POWER  FOR  DIFFERENT  NATIONS. 


Country. 


France  and  Baden 

Saxony 

Wurtemberg  

Prussia , 

Hanover 

England , 

Austria 


■      "d 

(fl-a 

cflTS 

m-d 

cn-O 

l^i 

tn-O 

e?3^ 

•c  C 

•a  c 

S  ,  c  0 

CO  C 

^-0  C 

ceo 

C  G  0 

oj  C  0 

Jr,  f=  ° 

1^  c  0 

<U   3   U 

030 

OJ  bjC3  0 

■3;  3   " 

w  3  0 

;_      3     0 

PI 

IV:. 

?nn 

nr:. 

sa^ 

l%z 

4J  w 

i^t 

^  at 

^itt 

S:^t 

75 

500 

529.68 

521-58 

477-93 

513-53 

542-47 

75 -045 

500-30 

530 

523-89 

478.22 

513-84 

542.80 

75-240 

501-36 

531.12 

525 

479-23 

514-92 

543-95 

75-325 

502.17 

531-97 

525-85 

480 

5^5-75 

544-82 

75-361 

502.41 

532.23 

526.10 

480.23 

516 

545-08 

76.041 

506.94 

537-03 

530.84 

484-56 

520.65 

550 

76.119 

507.46 

537-58 

531-39 

485.06 

521.19 

550.57 

CtI  C 
2  C  O 
'^  3  U 


423.68 
423-03 
424.83 
425-51 
425-72 
429.56 


ENERGY  AND  ITS    TRANSFORMATIONS.  1 7 

kilogrammetres  :  the  total  work  so  measured  is  then 
divided  by  the  time  of  operation  and  by  the  value  of 
the  horse-power  for  the  assumed  unit  of  time  and  the 
mean  value  of  the  power  expended  thus  finally  ex- 
pressed in  horse-powers.* 

The  forces  acting  in  machines  are  distinguished  into 
driving  and  resisting  forces.  That  component  of  the 
force,  acting  to  produce  motion  in  any  part  which  lies  in 
the  line  of  motion  only,  is  that  which  does  the  work ; 
and  this  component  is  distinctly  called  the  *'  Effort." 
Similarly,  only  that  component  of  the  resistance  which 
lies  in  the  line  of  motion  is  considered  in  measuring 
the  work  of  resistance.  In  either  case,  if  the  angle 
formed  between  the  directions  of  the  motion  of  the 
piece  and  of  the  driving  or  the  resisting  force  be  called 
o',  the  effort  is 

P  —  R  cos  a, (12) 

The  other  component,  acting  at  right  angles  to  the 
path  of  the  effort,  is 

Q  =  Rs\na, (13) 

and  has  no  useful  effect,  but  produces  waste  of  power 
by  introducing  lateral  pressures  and  consequent  friction. 

Energy,  which  is  defined  as  capacity  for  performing 
work,  is  either  actual  or  potential. 

Actual  or  Kinetic  Energy  is  the  energy  of  an  actually 
moving  body,  and  is  measured  by  the  work  which  it  is 
capable  of  performing  while  being  brought  to  rest, 
under  the  action    of   a  retarding  force  ;  this  work  is 

*  Custom  has  not  yet  settled  the  proper  form  of  the  plural  of  this 
word;  there  is  no  reason  why  it  should  not  follow  the  rule. 


1 8  THE  ANIMAL  AS  A    MACHINE. 

equal  to  the  product  of  its  weight,  W,  into  the  height, 

^'' 
h  —  — ,  throup;h  which  it  must  fall  under  the  action  of 

gravity  to  acquire  that  velocity,  v^  with  which  it  is  at 
the  instant  moving ;  i.e., 

E^U=^Wh^W~.       .     .     .     (14) 

A  change  of  velocity  i\  to  v^  causes  a  variation  of 
actual  energy,  E^  —  E^^  and  can  be  effected  only  by 
the  expenditure  of  an  equal  amount  of  work — 

E,-E^^U^w''^^-^=W{Ji,-h:).    (15) 

This  form  of  energy  appears  in  every  moving  part  of 
every  machine,  and  its  variations  often  seriously  affect 
the  working  of  mechanism. 

The  total  actual  energy  of  any  system  is  the  algebraic 
sum  of  the  energies,  at  the  instant,  of  all  its  parts ;  i.e., 

E^:2W—', (16) 

and  when  this  energy  is  all  reckoned  as  acquired  or  ex- 
pended at  any  one  point,  as  at  the  driving-point,  the 
several  parts  having  velocities,  each  n  times  that  of  the 
driving-point,  which  latter  velocity  is  then  v,  the  total 
energy  becomes 

E^^w'^y- (17) 

Actual  energy  is  usually  reckoned  relatively  to  the 
earth  ;  but  it  must  often  be   reckoned  relatively  to  a 


EXERGY  AND  ITS    TRANSFORMATIONS.  1 9 

given  moving  mass,  in  which  case  it  measures  the  work 
which  the  moving  body  is  capable  of  doing  upon  that 
mass,  when  brought  by  it  to  its  own  speed. 

Potential  Energy  is  the  capacity  for  doing  work  pos- 
sessed by  a  body  in  virtue  of  its  position,  of  its  condi- 
tion, or  of  its  intrinsic  properties.  Thus,  a  weight 
suspended  at  a  given  height  possesses  the  potential 
energy,  in  consequence  of  its  position,  E  =  Wh,  and 
may  do  work  to  that  amount  while  descending  through 
the  height,  //,  under  the  action  of  gravity.  A  bent 
bow  or  coiled  spring  has  potential  energy,  which 
becomes  actual  in  the  impulsion  of  the  arrow  or  is  ex- 
pended in  the  work  of  the  mechanism  driven  by  the 
spring.  A  mass  of  gunpowder  or  other  explosive  has 
potential  energy  in  virtue  of  the  unstable  equilibrium 
of  the  chemical  forces  afTecting  its  molecules.  Food 
has  potential  energy  in  proportion  to  the  amount  of 
vital  and  muscular  energy  derivable  by  its  consumption 
and  utilization  in  the  human  or  animal  system.  These 
potential  energies  are  not  measured  by  the  observed 
actual  energies  derived  from  these  substances  in  any 
case,  but  are  the  maximum  quantities  possibly  obtain- 
able by  any  perfect  system  of  development  and  utiliza- 
tion. In  practical  application,  more  or  less  waste  is 
always  to  be  anticipated. 

Every  instance  of  disappearance  of  actual  energy  in- 
volves the  performance  of  work,  and  the  production  of 
potential  or  of  some  new  form  of  actual  energy  in 
precisely  equal  amount.  A  stone  thrown  vertically  up- 
ward loses  kinetic  energy  as  it  rises,  in  precisely  the 
amount — resistance  of  the  air  being  neglected — by 
which  it  gains  potential  energy.  A  falling  mass  striking 
the  earth  surrenders  the  actual  energy  acquired  by  loss 


20  THE  ANIMAL  AS  A   MACHINE. 

of  potential  energy  during  its  fall,  and  the  equivalent 
of  the  quantity  so  surrendered  is  found  in  the  work 
done  upon  the  soil  ;  it  finally  passes  away  as  the  equiv- 
alent energy  of  heat  motion  produced  by  friction  and 
impact.  The  potential  chemical  energy  of  the  explo- 
sive is  the  equivalent  of  the  kinetic  energy  of  the  flying 
projectile,  and  the  latter  has  its  equivalent  in  the  work 
done  at  the  instant  of  striking  and  coming  to  rest,  and 
in  the  heat  produced  by  the  final  change  of  mass- 
motion  into  molecular  or  heat  motion. 

Work  may  be  defined  as  that  operation  which  re- 
sults in  a  change  in  the  method  of  manifestation  of 
energy,  and  Energy  as  that  which  is  transferred  or 
transformed,  when  work  is  done.  The  motion  of  a 
projectile  is  the  transfer  of  energy  from  one  place  to 
another.  It  is  generated  at  the  point  of  departure, 
stored  as  actual  or  kinetic  energy,  transferred  to  the 
point  of  destination,  and  there  restored  and  applied  to 
the  production  of  work. 

Acceleration  and  retardation  of  masses  in  motion 
can  only  be  produced  by  doing  work  upon  them,  or  by 
causing  them  to  do  work,  and  thus,  by  the  communi- 
cation of  energy  to  them  or  by  its  absorption  from  them, 
in  precisely  the  amount  which  measures  the  variation 
of  their  actual  energy  as  so  produced.  Every  body 
which  is  increasing  in  velocity  of  motion  thus  receives 
and  stores  energy  ;  every  mass  undergoing  retardation 
must  perform  work,  and  thus  must  restore  energy  pre- 
viously communicated  to  it.  In  every  machine  which 
works  continuously,  and  in  which  parts  are  alternately 
accelerated  and  retarded,  energy  is  stored  at  one  period 
and  restored  at  another,  in  precisely  equal  amounts. 

Work  done  upon  any  machine  may  thus  be  expended 


ENERGY  AND  ITS    TRANSFORMATIONS.  21 

partly  in  doing  the  useful  work  of  the  system,  and 
partly  in  storing  energy ;  and  the  same  machine  may 
do  work  at  another  instant  partly  by  expending  the 
energy  received  by  it,  and  partly  by  expending  stored 
energy  previously  accumulated. 

Storage  or  restoration  of  energy  thus  always  occurs 
when  change  of  speed  takes  place.  It  is  evident,  since 
the  storage  or  restoration  of  energy  implies  variation 
of  speed,  that  the  condition  of  uniform  speed  is  that 
the  work  done  upon  the  machine  shall  at  each  instant 
be  precisely  equal  to  that  done  by  it  upon  other  bodies. 
The  work  applied  must  be  equal  to  that  of  resistance 
met  at  the  driving-point.     Thus, 

2Pv  —  2Rv'',fPdv=fRdv'',      .     .     (i8) 

and  the  effort  at  each  point  in  the  machine  will  be 
equal  to  the  resistance,  and  will  vary  inversely  as  the 
velocity  of  the  point  to  which  it  is  applied  ;  i.e., 

P       v' 

P'^v (^9) 

In  the  starting  of  every  machine,  energy  is  stored 
during  the  whole  period  of  acceleration  up  to  maximum 
speed,  and  this  energy  is  restored  and  expended  while 
the  machine  is  coming  to  rest  again.  This  latter  quan- 
tity of  energy  is  usually  expended  in  overcoming  fric- 
tion. 

The  useful  and  the  lost  work  of  a  machine  are,  to- 
gether, equal  to  the  total  amount  of  energy  expended 
upon  the  machine,  i.e.,  to  the  work  done  upon  it  by  its 
'driver."  The  Useful  \Vork\?>  that  which  the  machine 
is  designed  to  perform  ;  the  Lost  Work  is  that  which  is 


22  THE  ANIMAL   AS  A   MACHINE. 

absorbed  by  the  friction  and  other  prejudicial  resist- 
ances of  the  mechanism,  and  which  thus  wastes  energy 
which  might  otherwise  be  usefully  applied.  These  two 
quantities,  together,  constitute  the  Total  Work  or  the 
Gross  Work  of  a  machine,  or  of  a  train  of  mechanism. 
In  every  case  some  energy  is  wasted,  and  the  work  done 
by  the  machine  is  by  that  amount  less  than  the  work 
performed  in  driving  it.  In  badly  proportioned  ma- 
chines the  lost  work  is  often  partly  expended  in  the 
deformation  and  destruction  of  the  members  of  the 
construction  ;  in  well-designed  and  properly  worked 
machinery  loss  occurs  wholly  through  friction.  In  ma- 
chines acting  upon  fluids  this  work  is  usually  partly 
wasted  in  the  production  of  fluid  friction — i.e.,  of  cur- 
rents and  eddies ;  thus  producing  new  forms  of  actual 
energy  in  ways  which  are  not  advantageous  :  even  this 
waste  energy  is  finally  converted,  like  the  preceding 
form,  by  molecular  friction,  into  heat,  and  is  dissipated 
in  that  form  of  molecular  energy.  Thuc  all  wasted 
work  is  lost  by  conversion  from  the  energy  of  mass- 
motion  into  molecular  energy,  and  ultimately  disappears 
as  heat. 

The  Efficiency  of  Mechanism  is  measured  by  the  quan- 
tity obtained  by  dividing  the  amount  of  useful  work 
performed,  by  the  gross  w^ork  of  the  piece  or  of  the  sys- 
tem. It  is  always,  therefore,  a  fraction,  and  is  less  than 
unity ;  which  latter  quantity  constitutes  a  limit  which 
may  be  approached  more  and  more  nearly  as  the  wastes 
of  energy  and  work  are  reduced,  but  can  never  be  quite 
reached.  If  the  mean  useful  resistance  be  R,  and  the 
space  through  which  it  is  overcome  be  s  ,  and  if  the 
mean  effort  driving  the  machine  be  P,  and  the  space 
through  which  it  acts  be  s,  the  total  and  the  net  or  use- 


ENERGY  AND  ITS   TRANSFORMATIONS.  23 

////  ivork  will  be,  respectively,  Ps^  Rs'\  the  lost  work 
will  be  Pt  —  Rs\  and  the 

Efficiency  =  -p-  <  i (20) 

Counter-efficiency  J  C,  is  the  reciprocal  of  the  effiency  ; 
i.e., 

Ps 

^=w (-) 

The  efficiency  and  the  counter-efficiency  of  a  machine, 
or  of  any  train  of  mechanism,  are  the  products  of  the 
efficiencies  or  of  the  counter-efficiencies  of  the  several 
elements  constituting  the  train  transmitting  energy 
from  the  point  at  which  it  is  received  to  that  at  which 
the  work  is  done,  i.e.,  from  the  "  driving "  to  the 
''  working  "  point. 

Friction  is  the  principal  cause,  and  usually  the  only 
cause,  of  loss  of  energy  and  waste  of  work  in  machinery. 
A  given  amount  of  energy  being  expended  upon  the 
driving-point  in  any  machine,  that  amount  will,  in  ac- 
cordance with  the  principle  of  the  persistence  of  energy, 
be  transmitted  from  piece  to  piece,  from  element  to 
element,  of  the  machine  or  train  of  mechanism,  without 
diminution,  if  no  permanent  distortion  takes  place  and 
no  friction  occurs  between  the  several  elements  of  the 
train,  or  between  those  parts  and  the  frame  or  adjacent 
objects.  Temporary  distortion,  within  the  limit  of 
perfect  elasticity,  causes  no  waste  of  energy  ;  permanent 
distortion,  however,  causes  a  loss  of  energy  equal  to 
the  total  work  performed  in  producing  it.  But  perma- 
nent distortion  is  due  to  deficiency  of  strength  and  de- 
fective elasticity,  and  is  never  permitted  in  well-designed 


24  THE   ANIMAL   AS  A    MACHINE. 

machinery  properly  operated  ;  and  hence  the  important 
principle : 

In  engineering,  the  principles  of  pure  mechanism,  of 
theoretical  mechanics,  and  pure  theory  in  the  science 
of  energetics,  or  of  thermodynamics,  are  to  be  studied 
as  introductory  to  a  science  of  apphcation  in  which  all 
actions  and  all  calculations  are  to  be  considered  with 
reference  to  the  modifications  produced  by  the  wastes 
of  energy  and  the  alteration  of  the  magnitudes  and 
other  properties  of  forces  consequent  upon  the  occur- 
rence of  friction. 

7.  The  Laws  of  Energetics,  the  basis  of  the  science 
which  it  has  been  proposed  to  call  by  that  name,  are : 

(i)  T'Jie  Law  of  Persistence,  or  of  Conservation  of 
Energy : — Existing  energy  can  never  be  annihilated  ; 
and  the  total  energy,  actual  and  potential,  of  any  iso- 
lated system  can  never  change. 

This  is  evidently  a  corollary  of  that  grander  law, 
asserting  the  indestructibility  of  all  the  work  of  creation, 
which  has  already  been  enunciated. 

(2)  The  Law  of  Dissipation,  or  of  Degradation  of 
Energy : — All  energy  tends  to  diffuse  itself  through- 
out space,  with  a  continual  loss  of  intensity,  with  what 
seems,  now,  to  be  the  inevitable  result  of  complete  and 
uniform  dispersion  throughout  the  universe,  and,  con- 
sequently, entire  loss  of  availability. 

It  is  only  by  differences  in  the  intensity  of  energy, 
and  the  consequent  tendency  to  forcible  dispersion, 
that  it  is  possible  to  make  it  available  in  the  production 
of  work. 

(3)  The  Law  of  Transformation  of  Energy : — Energy 
may  be  transformed  from  one  condition  to  another, 
or  from  any  one  kind  or  state  to  any  other ;  changing 


ENERGY  AND  ITS   TRANSFORMATIONS.  2$ 

from  mass-energy  to  molecular  energy  of  any  kind,  or 
from  one  form  of  molecular  energy  to  another,  with  a 
definite  quantivalence. 

These  laws  lead  to  the  conclusion  that,  in  any  iso- 
lated system  of  bodies,  or  in  any  isolated  mass,  the 
total  of  all  energy  present  is  always  the  same  ;  though 
it  may  be  transformed  in  various  ways,  and  to  an  ex- 
tent only  limited  by  the  special  conditions  affecting  the 
system.  They  lead  to  the  conclusion  that  energy  of 
higher  intensity  than  the  mean  must  occupy  a  limited 
space,  and  will  continually  tend  to  dissipate  itself  by 
dissemination  through  a  greater  volume,  affecting 
larger  and  larger  quanties  of  matter,  with  proportional 
reduction  of  intensity,  until  the  whole  system  is  occu- 
pied by  the  originally  existing  energy,  at  a  finally  uni- 
form and  minimum  intensity.  Energy  confined  within 
a  limited  space  thus  continually  tends  to  expand,  and 
to  break  through  its  boundaries,  and,  if  not  freed  from 
this  constraint,  it  produces  a  pressure  upon  the  sur- 
rounding surfaces,  which,  e.g.,  is  exhibited  as  tension 
of  enclosed  vapors  and  gases.  Freed  from  confine- 
ment, it  tends  to  indefinitely  expand. 

Either  form  of  energy  may  produce  either  other  form 
under  suitable  conditions. 

Rankine's  statement  of  the  *'  General  Law  of  the 
Transformation  of  Energy  "  is  as  follows  :  * 

*'  The  effect  of  the  whole  actual  energy  present  in  a 
substance,  in  causing  transformation  of  energy,  is  the 
sum  of  the  effects  of  all  its  parts." 

The  axiom,  as  Rankine  calls  it,  that  ''  any  kind  of 
energy  may  be  made  the  means  of  performing  any  kind 

*Proc,  Phil.  Soc.  of  Glasgow  ;  vol.  in.  No.  5  ;   1S53. 


26  THE  ANIMAL   AS  A    MACHINE. 

of  work  "  is  derived  by  ''  induction  from  experiment 
and  observation,"  and  confirmed  by  all  experience. 

TJie  Sources  of  Enej-gy  are  :  (i)  Potential :  {a)  fuel ;  {h) 
food ;  {c)  head  of  water ;  id)  chemical  forces.  (2) 
Actual :  {a)  air  in  motion  ;  {b)  gravity  in  waterfalls ;  (<:) 
tides. 

8.  "Newton's  Laws "  follow  directly  from  the  gen- 
eral law  of  persistence  of  energy,  a  corollary  to  which 
may  be  stated  thus  :  Change  of  energy  can  only  be  pro- 
duced by  the  action  of  force,  and  by  doing  work. 
Newton  s  Laws  are  : 

(i)  A  free  body  tends  to  continue  in  the  state  in 
which  it,  at  any  instant,  exists,  either  of  rest  or  of  uni- 
form rectilinear  motion. 

(2)  All  change  of  motion  in  a  body  free  to  move  is 
proportional  to  the  force  impressed,  and  is  in  the  direc- 
tion of  that  force. 

(3)  The  reaction  of  the  body  acted  upon  by  the  im- 
pressed force  is  equal,  and  directly  opposed,  to  that 
force. 

Inertia  is  that  property,  observed  in  all  bodies,  in 
consequence  of  the  existence  of  which  they  are  capable 
of  exhibiting  the  action  of  these  laws.  The  laws  of 
Newton  themselves  are  all  easily  verified  by  experiment. 
The  "Atwood  Machine,"  illustrated  in  nearly  all  works 
on  physics,  is  constructed  for  this  special  purpose. 

While  Newton's  laws  are  readily  verified  by  experi- 
ment, the  more  general  laws  of  energetics  are  accepted 
simply  as  being  in  accordance  with  universal  experience. 
The  generally  accepted  theory  of  the  constitution  of 
matter  being  assumed  as  a  premise,  however,  the 
general  laws  of  energy  are  all  easily  deducible  from 
Newton's   laws.     Thus,  the    first    law   is  but  a   differ- 


ENERGY  AND  ITS   TRANSFORMATIONS.  2y 

ently  worded  statement  of  Newton's  three  laws  com- 
bined. 

To  assert  that  every  moving  body  tends  to  persist  in 
its  rate  of  motion,  exerting  an  effort  always  equal  to 
the  retarding  or  accelerating  force,  and  exerting  such 
effort  in  the  line  of  action  of  such  force,  is  to  assert 
that  its  energy  can  only  be  altered  by  the  performance 
of  an  equivalent  amount  of  work,  and  an  equal  amount 
of  energy  of  opposite  sign  ;  and  this  latter  assertion  is  a 
declaration  of  the  indestructibility  of  energy.  To  assert 
that  all  bodies,  whether  masses  or  molecules,  when  in 
motion  tend  to  move  in  rectihnear  paths,  is  to  assert  a 
tendency  to  unlimited  dissipation  of  energy  through 
space.  To  assert  that  all  matter  in  motion  is  subject  to 
Newton's  laws  is  to  assert  the  laws  of  universal  conserva- 
tion of  energy,  and  of  the  quantivalence  of  all  transforma- 
tions, as  stated  in  the  third  general  law.  Whenever  it 
becomes  established  that  any  phenomenon,  as  the  trans- 
fer of  heat,  of  light,  of  electricity,  or  of  sound,  is  a  mode 
of  motion  affecting  bodies  of  whatever  class,  Newton's 
laws  bring  that  phenomenon  within  the  scope  of  the 
general  laws  of  energy.  Every  phenomenon,  molecu- 
lar or  other,  which  involves  relative  motion  of  masses, 
vibrations  of  parts,  or  pulsations  in  fluid  media,  is  now 
well  understood  to  be  subject  to  these  laws. 

9.  Algebraic  Expressions  of  the  transformability 
of  the  energies  are  now  readily  deduced.  If  in  any 
isolated  system  a  certain  quantity  of  energy  exists, 
homogeneous  in  character  and  heterogeneously  dis- 
tributed ;  and  if,  by  any  process,  other  and  various 
forms  of  energy  appear  in  that  system,  these  latter 
must  be  the  result  of  transformations  of  parts  of  the 
initial   stock    of   energy   by   conversion  into  the  new 


28  THE  ANIMAL  AS  A   MACHINE. 

forms.  But  every  such  change  must  be  effected  by  a 
perfectly  definite  and  exact  quantivalence. 

Assuming  this  ratio  of  values  of  customary  units 
reduced  to  a  system  of  equivalents,  it  becomes  at  once 
practicable  to  measure  all  these  energies  in  the  same 
units  ;  as,  for  example,  when  Joule  measures  either 
heat  or  mechanical  energy,  taking  y  =  778  foot-pounds, 
as  the  equivalent  of  a  British  thermal  unit,  ox  J  =  about 
427  kilograrnmetrcs,  as  the  equivalent  of  one  calorie  or 
metric  thermal  unit ;  the  thermal  unit  being  defined  as 
the  quantity  of  heat  or  energy-equivalent  demanded  to 
raise  the  temperature  of  unit  weight  of  water  one 
degree  from  the  temperature  of  maximum  density. 

Taking  either  kind  of  unit  in  thus  measuring,  we 
shall  have  the  initial  stock  of  the  one  kind  of  energy 
altered  by  the  quantity  which,  in  the  same  units, 
measures  the  aggregate  several  quantities  of  energy 
resulting  from  the  change  ;  and 

where  E,  T,  U,  V,  etc.,  are  the  symbols  representing 
the  several  energies,  initial  and  other. 

If  T  measure  heat-energy,  and  U  be  taken  as  poten- 
tial energy  of  the  molecular  kind,  V  the  potential 
energy  of  an  elastic  fluid  varying  in  volume,  W  the 
work  of  some  mechanism  or  a  dynamic  process,  the 
total  variation  of  the  initial  energy  E,  will  be  equal 
to  the  total  of  all  the  new  energies  and  the  new  work, 
in   proportions  which  become  known   as  soon  as  the 

dE 
partial  coefficients -—,  etc.,  are  determined. 


ENERGY  AND  ITS    TRANSFORMATIONS.  29 

If  two  energies  only,  as  thermal  and  mechanical,  are 
affected,  and  if  the  original  stock  were  simply  heat- 
energy,  we  should  have  a  change,  dE^  in  the  initial 
stock  of  heat-energy,  which  would  be  the  precise 
equivalent  of  the  sum  of  the  two  changes  taking  place, 
simultaneously,  in  the  initial  store  and  in  the  tempera- 
ture, T,  of  the  system,  and  in  work  by  the  change  of 
volume,  F,  against  a  pressure  of,  say,  the  intensity/. 
Then,  obviously, 

dE  dE 


and,  since  [-77^     measures   the  specific   heat,   K^,  for 

constant  volume,  and  as  (-ttv)     must    measure    the  in- 

\dVJ  T 


tensity  of  pressure  producing,  or  resisting,  the  change 
of  volume, 

dE  =  KJT^pdV. (2) 

If  but  one  kind  of  transformation  occurs,  as  by  con- 
version of  any  original  form  of  energy,  E,  into  work, 
a  process  illustrated  in  every  purely  thermodynamic, 
thermo-electric,  or  electro-dynamic  operation, 

dE^pdV\  ox,  dE^RdS.     ...     (3) 

Whatever  the  method  of  transformation  of  actual 
energy,  it  is  simply  a  process  of  transfer  of  the  energy 
of  motion  from  one  kind  of  matter  to  another,  or  from 
a  mass  to  a  collection  of  molecules,  with,  usually,  modi- 
fication of  the  mode  of  motion,  as  from  rectilinear  to 
vibratory,  or  from  motion  in  an  orbit  of  one  form  to 
m.ovement  in  a  path  of  different  character. 


30  THE  ANIMAL   AS  A    MACHINE, 

10.  The  Object  of  all  Mechanism  is  to  produce 
a  certain  definite  motion  of  some  part  or  parts — the 
position  and  form  and  the  methods  of  connection  of 
which  are  known  and  fixed — against  any  resistance 
that  may  be  met  with  in  the  course  of  such  movement. 
Every  machine  and  every  train  of  mechanism  is  there- 
fore a  contrivance  by  means  of  which  energy  or  power 
available  at  one  point,  usually  in  definite  amount  and 
acting  in  a  definite  direction  and  with  definite  velocity, 
is  transferred  to  other  points,  there  to  do  work  of 
definite  amount,  and  there  to  overcome  known  resist- 
ances with  known  velocities. 

The  object  of  the  engineer  in  designing  mechanism 
is  to  effect  this  transfer  of  energy  and  these  trans- 
formations at  the  least  cost  and  with  least  "  running 
expense,"  and  hence  with  maximum  efificiency  of 
apparatus.  It  is  often  important  to  secure  minimum 
volume  and  weight  of  machine,  as  well  as  maximum 
effectiveness  in  operation. 

The  work  of  a  machine  is  measured  by  the  magnitude 
of  the  resistance  encountered  and  the  velocity  with 
which  it  is  overcome.  The  nature  of  the  work,  aside 
from  its  simple  kinetic  character,  is  as  widely  variable 
as  are  the  details  of  human  industry. 

Prime  Movers  are  those  machines  which  receive 
energy  directly  from  natural  sources,  and  transmit  it 
to  other  machines  which  are  fitted  for  doing  the  various 
kinds  of  useful  work.  Thus,  the  steam-engine  derives 
its  power  from  the  heat-energy  liberated  by  the  com- 
bustion of  fuel ;  water-wheels  utilize  the  energy  of 
flowing  streams ;  windmills  render  available  the  power 
of  currents  of  air  ;  the  voltaic  battery  develops  the 
energy  of  chemical  action   in   its  cells  ;  and,  through 


ENERGY  AND  ITS    TRANSFORMATIONS.  3 1 

the  movement  of  electro-dynamic  mechanism,  this 
energy  is  communicated  to  other  machinery,  and  thus 
caused  to  do  work. 

]\IacJiincry  of  Transmission  is  used  in  the  trans- 
formation of  energy  supphed  by  the  prime  mover  into 
available  form,  for  the  performance  of  special  kinds  of 
work,  or  for  simple  transmission  of  power  from  the 
prime  mover  to  machines  doing  that  work. 

II.  The  Sources  of  Energy,  applied  by  man, 
through  the  prime  movers,  to  the  economic  purposes  of 
life,  are  six  in  number  : 

(i)  The  potential  energy  of  fuel,  coming  of  the  stor- 
age, in  early  geological  periods,  of  the  actual  energy  of 
the  heat,  light,  and  chemical  forces  of  the  sun's  rays, 
and  the  energy  of  the  dispersing  internal  heat  of  the 
earth,  gathered  up  by  the  vegetation,  and,  in  case  of 
the  mineral  oils,  possibly,  by  the  animal  life,  of  those 
primitive  ages,  reduced  to  this  potential  form  and  stored 
in  the  depths  of  the  earth  for  use  in  modern  times. 
Very  possibly  a  still  earlier  history  of  this  energy 
may  be  traced  in  the  gradual  transformation  of  the 
potential  dynamic  energy  of  a  chaotic  universe,  in- 
finitely dispersed,  into  the  heat-energy  of  collision  of 
particle  with  particle,  and  of  globe  with  globe,  as  the 
existing  systems  of  worlds  took  form.  The  potential 
energy  of  fuel  is  converted  by  combustion  into  active 
form. 

(2)  The  dynamic,  the  kinetic,  energy  of  falling  water, 
transferred  through  water-wheels  without  transforma- 
tion, to  do  useful  work. 

This  has  a  similar  origin  to  the  preceding  ;  the  water 
being  raised  from  the  seas,  lakes,  and  streams  to  the 
clouds  by  the  action  of  the  heat  of  the  sun,  thus  carried 


32  THE  ANIMAL  AS  A   MACHINE. 

to  the  higher  portions  of  the  land,  again  to  return  in 
the  streams  to  the  sea-level. 

(3)  The  kinetic  energy  of  the  air-currents,  as  utilized 
by  windmills,  which  convert  it  to  useful  purposes  pre- 
cisely as  the  water-wheel  intercepts  the  energy  of  fall- 
ing water  with  a  similar  end. 

The  primary  source  of  this  energy  is  again  the  heat 
of  the  sun,  which  produces  a  convection  of  air-cur- 
rents similar  dynamically,  in  method  and  result,  to 
those  of  water  in  the  ocean  or  over  or  on  the  land. 

(4)  The  energy  of  the  tides,  the  rise  and  fall  of  which 
constitute  a  source  of  power  less  easy  of  utilization 
than  that  of  streams,  and  for  this  reason,  rarely  applied 
to  the  production  of  power. 

The  origin  of  this  energy  is  in  the  force  of  gravita- 
tion as  it  acts  upon  the  ocean,  changing  its  level  through 
the  attractions  of  the  sun  and  the  moon.  This  is  seen 
to  be  essentially  different  from  the  other  cases. 

(5)  The  energy  of  electricity,  originally  exhibited 
either  in  the  form  of  molecular  energy  resulting  from 
chemical  action,  or  produced  by  transformation  directly 
from  the  dynamic  form.  In  this  latter  case,  the  ma- 
chine transforming  it  is  an  intermediate  or  a  secondary, 
instead  of  a  prime,  motor.  In  the  former  case  the 
origin  is  potential,  in  the  latter  kinetic. 

(6)  The  energy  of  muscular  action,  the  power  of  ani- 
mals, derived  from  the  chemical  forces  acting  in  the 
production  of  vegetation  and  transformed  for  use  in  the 
animal  system,  through  either  thermo-electric  or  thermo- 
dynamic processes,  or  perhaps  through  the  action  of 
both,  each  having  its  appropriate  task. 

In  the  animal  system,  the  vegetable  matter  employed 
as  food  is  converted  by  the  natural  forces  of  digestion 


ENERGY  AND  ITS    TRANSFORMATIONS.  33 

and  nutrition  into  available  form  for  use  by  the  nervous 
and  muscular  systems  of  the  body,  by  means  of  inter- 
mediate processes  which  are  as  yet  obscure.  It  is  only 
certain  that  they  cannot  all  be  thermodynamic  pro- 
cesses ;  it  seems  probable  that  they  are,  in  some  cases, 
at  least,  related  to  the  electrical  methods  of  transforma- 
tion. In  some  instances,  as  in  the  carnivora,  the  final 
conversion  results  from  a  double  transformation. 

Thus  substantially  all  utilized  natural  energy  is  de- 
rived, directly  or  indirectly,  from  the  sun. 

According  to  Sir  William  Thomson,  ''  the  mechanical 
value  of  a  cubic  mile  of  sunlight  is  12,050  foot-pounds, 
equivalent  to  the  work  of  one  horse-power  for  a  third 
of  a  minute.  This  result  may  give  some  idea  of  the 
actual  amount  of  mechanical  energy  of  the  luminiferous 
motions  and  forces  within  our  own  atmosphere. 
Merely  to  commence  the  illumination  of  three  cubic 
miles  requires  an  amount  of  work  equal  to  that  of  a 
horse-power  for  a  minute  ;  the  same  amount  of  energy 
exists  in  that  space  as  long  as  Hght  continues  to  traverse 
it ;  and,  if  the  source  of  light  be  suddenly  stopped, 
must  be  emitted  from  it  before  the  illumination 
ceases."  * 

The  same  authority  says :  "  Taking  the  estimate 
2781  thermal  units  centigrade,  or  3,869,000  foot-pounds, 

*The  mechanical  value  of  sunlight  in  any  space  near  the  sun's  sur- 
face must  be  greater  than  in  an  equal  space  at  the  earth's  distance,  in 
the  ratio  of  the  square  of  the  earth's  distance  to  the  square  of  the  sun's 
radius,  that  is,  in  the  ratio  of  46,400  to  i,  nearly.  The  mechanical 
value  of  a  cubic  foot  of  sunlight  near  the  sun  must,  therefore,  be  about 
,0038  of  a  foot-pound,  and  that  of  a  cubic  mile  560,000,000  foot-pounds. 
Similarly  we  find  15,000  horse-power  for  a  minute  as  the  amount  of 
work  required  to  generate  the  energy  existing  in  a  cubic  mile  of  light 
near  the  sun. —  Thomson. 


34  THE  ANIMAL  AS  A   MACHINE. 

as  the  rate  per  second  of  emission  of  energy  from  a  square 
foot  of  the  sun's  surface,  equivalent  to  7000  horse- 
power,* we  find  that  more  than  0.42  of  a  pound  of  coal 
per  second,  or  1500  lbs.  per  hour,  would  be  required 
to  produce  heat  at  the  same  rate.  Now  if  all  the  fires 
of  the  whole  Baltic  fleet  were  heaped  up  and  kept  in 
full  combustion  over  one  or  two  square  yards  of  surface, 
and  if  the  surface  of  the  globe  all  round  had  every  square 
yard  so  occupied,  where  could  a  sufficient  supply  of  air 
come  from  to  sustain  the  combustion  ? — yet  such  is  the 
condition  we  must  suppose  the  sun  to  be  in,  according 
to  the  hypothesis  now  under  consideration,  at  least  if 
one  of  the  combining  elements  be  oxygen  or  any  other 
gas  drawn  from  the  surrounding  atmosphere." 

12.  The  Forms  of  Motor,  the  special  machines 
through  which  these  transfers  and  transformations  are 
effected,  are  the  following : 

(i)  The  animal  body  is  a  vital  machine,  of  extra- 
ordinary complexity,  self-constructing  and  self-repair- 
ing, and  is  automatic  in  its  many  and  usually  mysterious 
internal  processes. 

This  machine  is  directed  by  conscious  intelligence 
and  will,  and,  when  usefully  applied  to  the  production 
of  work,  is  guided  by  the  mysterious  action  of  the  mind. 
It  effects  conversions  of  energy  through  the  processes 
of  chemical  action  peculiar  to  the  animal  system. 

(2)  TJie  heat-engines,  including  steam-,  air-,  gas-,  and 
vapor-engines  of  various  less  familiar  kinds. 

In  these  machines,  the  potential  energy  of  fuel  is,  by 
combustion,  converted  into  the  active  form,  and  stored 

*  This  is  sixty-seven  times  the  rate  at  which  energy  is  emitted  from 
the  incandescent  electric  lamp  at  the  temperature  which  gives  240 
candles  per  horse-power. 


ENERGY  AND  ITS    TRANSFORMATIONS.  35 

in  a  gaseous  or  vaporous  fluid,  the  variations  of  tem- 
perature, pressure,  and  volume  of  which  result  in  the 
production,  more  or  less  efficiently,  of  mechanical  power 
in  readily  applicable  form. 

The  heat-engines  do  by  far  the  greater  part  of  the 
work  of  the  world,  and  the  steam-engine  the  main  por- 
tion of  that  performed  by  thermodynamic  operations. 

Solar  engines,  so-called,  are  heat-engines  in  which  the 
direct  heat  energy  of  the  sun,  instead  of  the  stored  heat 
energy  of  a  combustible,  is  utilized  through  the  action  of 
a  working  fluid,  as  with  other  forms  of  machine  of  this 
class. 

(3)  The  zvafer-wheels,  including  the  various  classes  of 
so-called  vertical  wheels,  and  the  turbines  ;  in  which 
latter,  the  water,  instead  of  entering  *'  buckets,"  to  be 
again  poured  out  of  them,  passes  continuously  through 
channels,  without  reversal  of  motion. 

These  machines  effect  no  transformations  of  energy ; 
but  simply  turn  it  out  of  its  natural  course  into  an  arti- 
ficial channel  of  application.  It  is  kinetic,  as  found, 
and  remains  kinetic  until  transformed  in  the  course  of 
its  application  to  its  intended  purpose. 

(4)  Tidal  viacJiines  are  simply  floats,  rising  and  fall- 
ing with  the  tides ;  or  they  are  vertical  water-wheels, 
working  in  tidal  currents  in  precisely  the  same  manner 
as  those  operated  by  ordinary  running  streams.  They 
transfer,  but  do  not  transform,  energy. 

(5)  Windmills  are  pneumatic  turbines,  especially 
fitted  to  take  up  the  energy  of  moving  air,  and  to  transfer 
it,  without  transformation,  to  machinery  of  transmission, 
through  which  it  is  conveyed  to  its  point  of  application. 

(6)  Electrical  engines,  electro-dynamic  machines, 
dynamos  and  motors,  as  they  are  variously  called,  are 


36  THE   ANIMAL  AS  A   MACHINE. 

apparatus  for  transformation,  converting  the  molecular 
energy  of  electricity  into  the  mechanical  form  in  such 
manner  as  permits  its  useful  employment. 

These  machines,  reversed,  change  the  energy  of  me- 
chanical power  into  the  electrical  form,  and  both  direc- 
tions of  transformation  in  well-designed  machinery 
result  in  a  very  efficient  conversion  of  energy.  As  a 
rule,  it  is  found  much  more  satisfactory  to  derive  the 
energy,  initially,  from  a  prime  mover,  by  conversion 
into  the  electrical  form,  than  to  obtain  it  directly  from 
the  voltaic  battery.  Water-power  or  the  combustion 
of  fuel  is  vastly  less  costly  than  the  combustion  of  zinc 
and  the  saturation  of  acids  with  its  salts. 

The  purpose  of  this  discussion  is  to  describe,  briefly 
and  exactly,  the  characteristics  of  the  animals  as  motors, 
to  describe  their  methods  of  action  and  their  sources  of 
gain  and  loss  of  energy,  and  to  present  the  principles 
of  energy-production  and  transformation  illustrated  by 
them. 


11. 


THE  ANIMAL  AS  A   MACHINE  AND  A   PRIME 
MOTOR. 

13.  The  Animal  as  a  Machine. — The  engineer  re- 
gards the  animal  system  with  peculiar  interest,  as  a 
machine  of  singularly  complicated  structure,  a  heat- 
engine  or  other  prime  motor — he  is  not  certain  as  to 
its  classification — of  extraordinary  efficiency,  and  as 
the  embodiment  of  scientific  problems  of  the  highest 
interest  and  greatest  obscurity.  In  this  curious  ma- 
chine, combustible  matter  in  the  form  of  the  grains  or 
other  foods,  is  consumed,  with  resultant  production  of 
carbon  dioxide  and  other  chemical  compounds  of 
various  degrees  of  oxidation,  and  there  is  thus  made 
available  thermal,  mechanical,  and  probably  electrical 
as  well  as  vital  energies,  all  of  which  energies  find 
application  in  the  processes  of  animal  life,  in  the  per- 
formance of  work,  external  and  internal,  and  probably 
in  mental  operations  as  well.  Waste  also  occurs  in 
the  form  of  heat  and  the  rejected  potential  energy  of 
incomplete  chemical  action. 

Considering  the  automatic  system  of  the  animal, 
apart  from  intelligence  and  will,  it  is,  in  the  eye  of  the 
engineer,  a  self-contained  prime  mover,  includifig  its 
furnace,  its  mechanism  of  work  and  energy-develop- 
ment, and  possessing  mechanism  of  transmission  of 
power  peculiarly  and  exactly  adapted  to  its  purposes. 

37 


38  THE  ANIMAL  ASA    MACHINE. 

14.  The  Animal  as  a  Prime  Motor.* — Hirn  was 
probably  the  first  and  the  greatest  of  those  who  have 
sought  to  measure  up  the  energies  of  hving  creatures, 
and  to  follow  the  transformations  which  occur  in  the 
processes  of  vital  organization  and  animal  exertion. f 

The  origin  of  heat  in  the  bodies  of  living  animals  has 
been  a  matter  awakening  the  greatest  interest  and 
curiosity  from  the  earliest  times.  The  ancients  thought 
heat  and  light  a  part  of  the  vital  power,  due  to  the 
creative  act,  and  without  immediate  source  in  the 
processes  of  vital  existence.  They  thought  the 
act  of  breathing  a  necessary  process  of  cooling  and 
removal  of  excess  of  this  spontaneously  generated 
heat,  due  to  the  fact  of  life  simply.  Since  the  estab- 
lishment of  the  principles  of  energy  in  modern  times, 
however,  the  philosopher  has  only  concerned  himself 
as  to  the  method  of  production  of  this  heat,  recogniz- 
ing the  fact  that  it  must  have  its  origin,  as  must  all  the 
exhibitions  and  expenditures  of  energy  that  accompany 
it  in  the  living  being,  from  the  potential  and  latent 
energies  of  combustible  substances  subjected  to  the 
processes  of  digestion  and  assimilation  in  the  body. 
The  scientific  man  of  later  times  sees  in  the  vital  pro- 
cesses a  transformation  of  energies  originating  in  a 
slow  combustion  at  low  temperature,  with  changes  of 
form  of  the  resulting  energies  which,  though  none  the 
less  certainly  phases  of  the  chain  of  vital  phenomena 
which  he  studies,  are  not  all  fully  understood,  or  as 
yet  all  detected  and  rendered  evident  by  research. 
The  chemical  compositions  of  these   combustibles  are 

*  From  Cassier's  Magazine,  Feb.,  1892;  by  R.  H.  Thurston. 
\  La  Thermodynamique  et  I'Etude  du  Travail  chez  les  Etres  vivants. 
G.  A.  Hirn,  Paris.     Bureaux  des  Revues,  1887. 


THE  ANIMAL  AS  A   MOTOR,  39 

known  ;  the  quantities  of  energy  which  may  be  ob- 
tained by  their  perfect  combustion  to  carbonic  acid 
and  water  are  well  ascertained,  and  it  only  remains  to 
determine  the  exact  nature  of  the  processes  by  which 
it  is  possible  to  effect  their  combustion  at  the  tempera- 
ture of  the  animal  system,  and  to  utilize  by  transform- 
ation the  resulting  power  through  those  intermediate 
forms  of  energy-change  which  remain  as  yet  undis- 
covered, and,  in  that  sense,  mysterious.  We  do  not 
yet  know  how  to  produce  combustion  at  a  temperature 
of  98°  Fahr.,  that  at  which  combustion  certainly  does 
occur  in  the  human  system  ;  or  at  the  still  lower  tem- 
peratures at  which  such  chemical  changes  go  on  in  the 
bodies  of  cold-blooded  creatures  ;  nor  do  we  know  how 
to  secure  transformation  of  heat  into  mechanical  and 
other  forms  of  energy  without  sensible  change  of  tem- 
perature and  with  high  efficiency.  In  all  our  uses  of 
heat-engines  the  wastes  are  a  much  greater  proportion 
of  the  available  energy  than  in  any  animal  system, 
except  where,  as  in  some  cases  of  application  of  the 
heat-energy  of  steam,  for  example,  the  wastes  of  the 
engine  are,  as  in  the  human  body,  utilized  for  heating 
purposes. 

The  muscles  when  doing  work,  and  all  the  glands, 
every  organ,  in  fact,  while  performing  its  legitimate 
function,  is  found  to  become  warmer ;  indicating  the 
final  appearance  of  whatever  .form  of  energy  may  be 
operating  in  the  system  in  the  form  of  heat.  Heat  is 
produced,  apparently,  in  all  the  organs  of  the  body,  but 
in  different  degree,  accordingly  as  their  action  is  intense 
or  deliberate.  Those  veins  which  return  blood  from 
working  organs  bring  it  back  slightly  warmer  than  the 
average  for  the  whole  system  ;  those  coming  in  toward 


40  THE  ANIMAL  AS  A   MACHINE. 

the  heart  from  the  skin  bring  back  colder  blood  from 
that  constantly  refrigerated  system  of  capillaries.  The 
mean  temperature  of  the  venous  blood  entering  the 
heart  is  about  one  degree  warmer,  in  man,  than  the  aver- 
age for  the  whole  system  ;  between  one  and  two  de- 
grees warmer  than  the  arterial  blood.  The  tempera- 
ture of  the  body,  as  a  whole,  is  automatically  regulated 
by  the  system  of  nerves  studied  by  Bernard  ;  which 
causes  the  flow  of  blood  toward  any  part  to  be  accel- 
erated when  that  part  is  cold,  and  retarded  when  it  is 
too  warm. 

In  every  mechanism  endowed  with  animal  life,  heat 
is  produced  and  work  is  performed.  It  by  no  means 
follows  that  the  work  is  the  result  of  thermodynamic 
transformation ;  in  fact,  it  seems  impossible,  in  view  of 
the  fact  that  we  have  in  the  animal  system  no  differ- 
ences of  temperature  such  as  characterize  and  limit  the 
action  of  the  thermodynamic  engine,  that  there  should 
be  a  thermodynamic  transformation.  The  heat  would 
seem  to  be  either  a  "by-product"  or  to  be  produced 
simply  to  insure  uniform  and  sufficient  temperature  to 
permit  the  continuous  and  steady  action  of  the  vital 
powers  and  the  machinery  of  the  body.  All  the  ali- 
mentary substances  are  combustible  ;  but  it  is  not  a 
necessary  consequence  that  they  should  be  oxidized  by 
a  heat-producing  combustion  within  the  animal  system. 
On  the  contrary,  the  quantity  of  heat  which  would  be 
thus  produced,  added  to  the  quantity  of  work  per- 
formed by  the  vital  organs,  in  digestion,  nutrition,  cir- 
culation of  the  blood, — itself  an  enormous  quantity, — 
though  reproducing  the  energy  thus  expended,  as  heat, 
and  thus,  in  one  sense,  costing  nothing — and  in  brain- 
work,  to    say  nothing    of   wastes  by   conduction  and 


THE  ANIMAL  AS  A   MOTOR.  4 1 

radiation  to  surrounding  objects,  the  total  amount  of 
heat  produced  by  such  combustion  would  vastly  ex- 
ceed the  quantity  discharged  from  the  body  in  any 
given  time.  This  discrepancy  is  greater  in  cold-blooded 
animals  than  in  warm-blooded ;  and,  in  many  in- 
stances, the  heat  given  out  is  probably  too  small  in 
amount  to  account  for  combustion  of  any  important 
fraction  of  the  aliment  of  the  system.  The  animal  ma- 
chine is  not  thermodynamic  in  the  usual  acceptation  of 
that  term,  even  if  it  be  in  any  sense. 

Mon.  J.  Beclard  was  probably  the  first  to  attempt  to 
measure  the  relation  of  quantity  and  of  transformation, 
thermodynamically,  if  such  energy-transformations 
actually  occur,  in  the  animal  machine.  But  he  reached 
no  definite  result.  Herdenheim  suceeded  little  better; 
but  Hirn  found  ways  of  investigation  which  gave  real 
quantitative  results  of  importance.  A  certain  corre- 
spondence was  found  between  work  performed  and 
heat  exhaled  ;  but  nothing  in  his  experiments  gave  in- 
dications of  the  method  of  production  of  that  heat  ;  and 
it  is  still  impossible  to  say  whether  the  heat  is  the  direct 
product  of  oxidation  of  food,  the  result  of  oxidation  of 
worn  muscular  and  other  tissue,  or  due  to  a  number  of 
thermal  and  other  interactions  occurring  within  the 
body  and  as  yet  beyond  the  reach  of  scientific  observa- 
tion. The  disappearance  of  heat  unquestionably  estab- 
lished by  Hirn's  researches  may  or  may  not  have  been 
due  to  thermodynamic  transformations.  Whatever 
form  of  energy-transformation  characterizes  the  vital 
machine,  the  wastes  of  energy  take  the  final  form  of 
heat,  and  its  quantity  would,  in  any  case,  be  reduced  by 
the  production  of  mechanical  energy  and  the  perform- 
ance of  work  within  and  without  the  body. 


42  THE  ANIMAL  AS  A   MACHINE. 

In  1856-57  Hirn  experimented  with  men  engaged  in 
regular  work  and  at  rest,  and  found  that  when  at  rest 
they  produced  a  quantity  of  heat  almost  exactly,  if  not 
precisely,  proportional  to  the  amount  of  oxidation,  as 
measured  by  the  quantity  of  oxygen  absorbed  by  them 
and  exhaled  in  carbonic  acid. 

This  was  not  precisely  the  case  when  they  were  at 
work.  The  principle  of  equivalence  of  energies  then 
takes  effect,  and  the  measure  of  all  the  energy  pro- 
duced by  oxidation  is  found  in  the  sum  of  the  heat 
discharged  from  the  system  and  that  energy  of  work 
which  stands  for  the  parts  converted  into  dynamic 
forms. ^ 

Hirn  found  that  the  quantity  of  heat  generated  by 
the  human  body  at  rest,  whether  that  of  men  of  mid- 
dle age,  or  youth  of  either  sex  approaching  maturity, 
was  substantially  the  same  under  the  same  circum- 
stances :  about  5  calories  per  gramme  of  oxygen  in- 
spired and  exhaled  as  a  minimum,  5.2  as  a  maximum, 
and  usually  the  latter  figure.  The  differences  may  be 
ascribed  to  variations  in  observations,  rather  than  to 
real  differences  of  fact.  Precisely  the  same  quantities 
of  air  were  measured  as  exhaled  as  were  measured  as 
inhaled,  in  all  cases.  A  singular  and  significant  fact 
was,  however,  discoverable  in  the  results,  as  reported 
by  Hirn  :  The  quantity  of  heat  produced  per  unit  of 
oxygen  absorbed  and  converted  into  compounds  ex- 
ceeds by  a  third  the  amount  computed  upon  the  basis 
of  the  experiments  of  Favre  and  Silbermann.  This 
result  would  seem  to  indicate  other  sources  of  heat 
than   combustion   with    oxygen.     It    may   be    due    to 

*  L'Equivalent  mecanique  de  la  Chaleur.     G.  A.  Hirn,  1858. 


THE  ANIMAL  AS  A   MOTOR.  43 

oxygen  absorbed  and  exhaled  through  the  skin  ;  to  the 
conversion  of  stored  energies  as  yet  undetected  in  the 
system  ;  or  to  the  combination  of  other  elements,  as 
carbon  and  hydrogen,  through  processes  resulting  in 
the  production  of  heat."^  It  is  to  the  latter  cause  that 
Hirn  would  ascribe  this  excess  of  exhaled  energy. 
This  subject  remains  still  to  be  investigated. 

The  same  individuals  being  set  at  hard  work  in  a 
treadmill  constructed  for  the  purpose,  in  such  manner 
as  give  the  figures  for  a  normal  condition  of  labor, 
unforced  but  steady,  and  at  a  maximum  for  a  day's 
work,  gave  out  but  about  one  half  as  much  heat  per 
unit  of  air  breathed  and  of  oxygen  consumed,  showing 
clearly  the  transformation  of  heat  into  work.  The 
efficiencies  of  the  human  system,  considered  as  a  heat- 
motor  or  -engine,  ranged,  according  to  the  condition 
and  temperament  of  the  subject  of  the  test,  from  17 
per  cent  to  25  per  cent  when  raising  the  load  or  them- 
selves ascending,  and  rose  to  30  and  40  per  cent  in 
descent.  A  lymphatic  youth  of  18  gave  the  lowest 
figures  ;  a  strong  man  of  47  the  highest.  These  results 
all  exceed  those  obtainable  as  yet  from  the  most  eco- 
nomical forms  of  existing  gas-  or  steam-engine,  in 
which  20  per  cent  may  be  taken  as  about  the  con- 
temporary limit  of  their  efficiency  as  heat-engines. 

To  fully  secure  this  efficiency  in  the  human  body  as  a 
heat-engine  subjected  to  the  accepted  laws  of  thermo- 
dynamics would  demand  a  temperature  within  its 
working  parts  not  far  from  140  Cent.  (284°  Fahr.),  or 
far  above  the  boiling-point  of  water.  This  fact  is 
crucial  as  a  proof  that  the  transformations  of  energy 

*  SeeSarason  :  Revue  Scientifique,  1SS7,  page  306  et  seq. 


44  THE  ANIMAL  AS  A   MACHINE. 

in  the  animal  system  are  not,  in  the  accepted  sense, 
thermo-dynamic.  They  must  involve  as  yet  unknown 
processes  and  methods,  and  must  be  free  from  the 
control  of  thermodynamic  principles,  as  we  are  accus- 
tomed to  denominate  them.  The  ''second  law  of 
thermo-dynamics  "  is  here  evaded. 

In  those  cases  in  which  work  was  done,  the  produc- 
duction  of  heat  was  as  much  less  than  that  anticipated, 
as  computed  from  the  engineers'  and  the  physicists* 
experiments,  as,  in  the  case  of  rest,  that  figure  was 
exceeded,  falling  in  the  latter  case  to  from  2.5  calories 
to  3.5  per  gramme,  varying  with  the  individual  and  his 
familiarity  with  the  work,  and  consequent  efficiency  as 
a  machine. 

Thus  the  investigator  shows  that  while  the  animal 
system  is  unquestionably  a  machine  producing  and 
utilizing  energy  by  transformation,  it  possesses  some 
peculiarities  and  conceals  some  secrets  that  science 
has  still  to  discover  through  exact  methods  of  research. 
It  further  has  become  evident  that  these  methods  of 
production  and  utilization  of  energy  include  some 
which  are  very  different  from  those  familiar  to  us,  as 
exhibited  in  our  inanimate  heat-engines,  and  which, 
once  discovered  and  given  application,  should  that 
prove  practicable  in  artificial  machines  of  this  class, 
will  probably  prove  enormously  advantageous  in  the 
saving  of  costly  energies  now  so  largely  wasted.  Could 
we  discover  and  apply  these  methods  in  displacing  our 
heat-engines,  it  would  give  us  direct  transformations  of 
energy  into  work  at  low  temperatures,  with  little  or  no 
wastes,  and  thus  enormously  extend  the  period  of 
human  life  on  this  globe,  as  well  as  its  productiveness. 
It  will  be  an   interesting  question   for  the  electrician 


THE  ANIMAL  AS  A   MOTOR.  45 

and  the  engineer  to  settle :  whether  these  as  yet 
mysterious  processes  are  not  electro-dynamic  or  related 
phenomena. 

15.  The  Processes  of  the  Vital  Machines  em- 
ployed in  the  development  of  power  result  mysteri- 
ously in  the  production  of  heat,  light,  electricity,  and 
dynamic  energy  by  methods  still  unknown,  and  with 
an  efficiency  of  development,  transformation,  and 
application  frequently,  if  not  always,  much  greater 
than  has  been  yet  attained  by  any  of  the  machines 
devised  by  man  to  effect  similar  results.  Mechanical 
power  is  exerted  at  less  cost  in  potential  energy  sup- 
plied than  in  the  steam-engine  ;  heat  is  evolved  as  the 
product  of  combustion  or  other  action  at  a  low  tem- 
perature, and  with  insignificant  waste  by  non-utilization 
in  the  processes  of  the  animal  economy ;  light  is  pro- 
duced by  glow-worms  and  fire-flies  without  sensible 
loss  in  accompanying  thermal  or  other  energy ;  and 
electricity,  probably  the  motor  energy  of  the  machine, 
is  produced  with  similar  wonderful  economy  by  pro- 
cesses of  which  we  have  no  knowledge.  Combustion 
at  ordinary  low  temperatures,  in  the  tissues  of  the 
body;  chemical  combinations  of  other  kinds  in  the 
digestive  organs,  by  the  action  of  peptic  substances  in 
solution  in  the  fluids  of  the  system,  and  other  pro- 
cesses unknown,  as  yet :  these  evade  the  inevitable 
losses  of  thermo-dynamic  operations  in  the  vital 
machine,  and  effect  results  which  are  never  economi- 
cally obtainable  by  the  machines  of  the  inventor  and 
mechanic.  These  constitute  a  standing  riddle  and 
challenge  to  the  man  of  science  and  the  engineer. 

Lavoisier,  as  early  as  1789,  asserted  that  animals  are 
composed  of  combustible  substances,  and  that  their  life 


46  THE  ANIMAL  AS  A    MACHINE. 

is  based  upon  chemical  action  involving  the  slow  com- 
bustion of  the  carbon  and  hydrogen  of  their  food  and 
muscle  ;  respiration  furnishing  the  needed  oxygen — an 
element  discovered  by  him  three  years  earlier.  Rum- 
ford,  in  1797,  stated  that  animals,  considered  as  ma- 
chines, were  efficient  prime  motors,  and  in  1799  pub- 
lished his  discovery  of  the  identity  of  heat  with  mechani- 
cal energy  and  his  approximation  to  the  value  of  the 
mechanical  equivalent ;  and  Scoresby  and  Joule,  and 
especially  Hirn,  later  completely  confirmed  his  views 
on  these  points.* 

Modern  research  shows  that  the  evolution  of  heat 
is  at  least  an  invariable  accompaniment  of  all  action  of 
the  animal  system — also  even  of  the  brain  and  spinal 
cord.  Thought  and  manual  labor,  in  the  case  of  the 
human  machine,  are  alike  productive  of  increased  tem- 
perature and  of  accelerated  exhalation  of  carbon  diox- 
ide from  the  lungs  and  of  salts  from  other  organs. 
Whether  these  chemical  actions  are  direct  results  or 
simply  incidental  to  intermediate  transformations  of 
matter  and  energy  is  as  yet  not  fully  determined. 
The  effect  of  exercise  is  invariably  to  increase  greatly 
the  consumption  of  oxygen,  and  the  elimination  of 
carbon  dioxide,  and  the  temperature  of  the  body,  within 
narrow  limits ;  regulation  being  effected  by  exudation 
of  perspiration  and  its  evaporation.  Other  effects  of 
increased  exertion  of  the  muscular  system  are  the  pro- 
motion of  digestion,  the  consumption  of  accumulated 
combustible  matter,  as  the  fats,  and  increased  rapidity 
and  thoroughness  of  blood  circulation  and  of  nutrition. 


*  On  these  points,  see  Seguin  and  Lavoisier  (Premier  Memoir),  Rum- 
ford's  Essays,  and  Philosophical  Magazine,  1846. 


THE  ANIMAL  AS  A   MOTOR.  47 

which  are  the  essentials  to  efficient  action  of  the  ma- 
chine as  a  whole.  The  wonderful  self-adjusting  power  of 
the  system  makes  these  actions  effective  even  locally ; 
and  the  exercise  of  one  member  or  part  of  the  machine 
produces  increased  circulation,  increased  degeneration, 
and  at  the  same  time  increased  blood-supply  and  nutri- 
tion of  the  part  thus  compelled  to  supply  energy. 

The  muscular  system  constitutes  about  40  per  cent 
of  the  weight  of  the  body,  and  contains  blood  to  the 
amount  of  one  third  this  weight,  or  12  to  15  per  cent 
of  the  whole  weight  of  the  body.  The  wear  of  this 
muscular  tissue  gives  rise  to  a  demand  for  the  nitro- 
genous foods  to  supply  the  waste,  and  thus  produces 
an  appetite  for  lean  meats  or  for  vegetable  foods  rich 
in  gluten.  The  nervous  tissue,  the  system  of  inter- 
communication and  transfer  of  energy  from  part  to 
part,  is  also  subject  to  wear  ;  and  this  waste  is  supplied 
by  the  phosphatic  foods,  as  animal  brain,  marrow,  nerve, 
and  glandular  or  other  white  meats,  and  as  the  fruits 
and  the  grain-foods,  the  peculiar  diet  of  the  human  and 
especially  of  the  brain-working  creature.  Overuse  of 
the  muscles  or  of  the  nervous  system  reduces  their 
powers  of  recuperation,  repair,  and  general  nutrition  ; 
and  it  is  for  this  reason  that  labor  and  exercise  should 
be  carefully  restricted  within  those  limits  marked  by 
the  appearance  of  symptoms  of  exhaustion.  Highest 
efficiency  of  the  animal,  as  of  any  other  machine,  can 
be  permanently  maintained  only  when  the  conditions 
of  maximum  perfection  of  parts  and  of  operation  are 
ascertained  and  insured.  The  selection  of  proper  foods 
is  as  essential  to  the  successful  maintenance  and  use  of 
the  animal  machine  as  the  securing  of  good  fuel  for  use 
in  the  heat-engines ;  attention  to  diet  and  the  adjust- 


48  THE  ANIMAL  AS  A   MACHINE. 

ment  of  the  periods  of  employment  to  best  effect  are 
as  important  as  the  supply  of  the  best  coal  and  the 
periodical  stoppage  and  repair  of  the  machinery  in  a 
mill  or  factory. 

The  elimination  of  nitrogen  and  carbon  dioxide  is,  in 
some  as  yet  uncertain  way,  a  gauge  of  the  quantity  of 
useful  and  lost  work  of  the  animal  machine.  Liebig 
states  in  his  Animal  Chemistry  (1843)  that  the  excre- 
tion of  nitrogen  is  proportional  to  the  destruction  of 
tissue,  and  Lehman  states  in  his  turn  that  he  finds  this 
excretion  increased  by  exercise.  Fick  and  Wislicenus, 
on  the  other  hand,  assert  that  the  animal  is  a  heat- 
engine,  and  that  the  performance  of  work  affects  the 
elimination  of  nitrogen  shghtly,  but  increases  that  of 
carbon  dioxide  enormously,  and  this  view  is  confirmed 
by  Frankland  and  by  Houghton ;  while  Dr.  Parkes  in- 
directly gives  similar  testimony  in  the  statement  that 
work  is  done  by  the  consumption  of  other  than  nitroge- 
nous foods,  the  elimination  of  nitrogen  being  due  to 
waste  of  tissue ;  that  of  carbonic  acid  to  combustion 
resulting  in  thermodynamic  action.  Incidentally, 
Liebig  also  confirms  this  idea  by  his  statement  that 
the  exhalation  of  nitrogen  goes  on  long  after  work  has 
ceased."^  Dr.  Pavy,  on  the  other  hand,  found  by  ex- 
periment on  two  well-known  pedestrians  that  their 
excessive  exertion  produced  greatly  increased  elimi- 
nation of  nitrogen — apparently  a  consequence  of  the 
breaking  down  of  tissue.  He  concludes  that  the  body 
is  a  true  heat-engine,  but  he  finds  it  capable  apparently 


*See  Frankland's  Origin  of  Muscular  Power;  Houghton  in  the 
Lancet,  1868  ;  Parkes  in  the  Medical  Times,  1871  ;  Flint  on  Muscular 
Power,  1872  ;  Pavy  on  Muscular  Power,  1878. 


THE  ANIMAL  AS  A    MOTOR.  49 

of  performing  more  work  than  the  food  would  seem 
competent  to  do.  In  these  cases  it  would  seem  very 
possible  that  the  observed  excess  may  come  of  con- 
sumption of  tissue  in  addition  to  food  ;  the  waste  being 
gradually  repaired  during  a  later  period  of  prolonged 
rest,  with  food-consumption  above  the  normal  rate. 

Dr.  Flint,  who  paid  much  attention  to  this  subject, 
concluded,  as  the  result  of  the  study  of  the  working  of  the 
muscular  system  of  a  celebrated  pedestrian  (Weston), 
about  1870,  during  a  walk  of  318  miles  in  five  days, 
weighing  all  foods  and  excretions  and  noting  their  com- 
position, that  it  is  as  yet  impracticable  to  intelligently 
compare  the  force-value  of  foods  with  the  work  of  the 
muscular  system  ;  that  such  estimates,  as  now  custom- 
arily made,  account  only  for  a  part  of  the  work,  even 
leaving  out  of  consideration  the  energy  of  other  (vital 
and  nervous)  actions ;  that  exercise  always  results  in 
waste  of  muscular  tissues,  which  may  not  be  repaired  at 
the  time  ;  and  he  also  beheves  that  the  source  of  energy 
is  the  wasted  tissue,  and,  indirectly  only,  the  nitrogen- 
ized  food  which  supplies  the  waste. 

Dalton  takes  the  production  of  heat  in  the  body  at 
rest,  per  hour,  as  about  1.28  British  heat-units  per  pound 
of  its  weight.  Houghton  estimates  the  work  done  in 
walking  at  one  twentieth  of  the  weight  of  the  body  in 
pounds  multiplied  by  the  number  of  feet  walked  per 
hour ;  and  it  would  seem  possible,  from  Flint's  compu- 
tations, that  about  ten  per  cent  of  the  total  energy- 
expenditure  takes  place  in  the  brain  and  nervous  sys- 
tem in  the  case  of  man,  although  that  author  does  not 
so  take  it.*     The  processes  involved  in  the  operation 

*  Source  of  Muscular  Power,  pp.  100-103. 


50  THE   ANIMAL  AS  A   MACHINE. 

of  the  animal  mechanism,  to  say  nothing  of  its  mental 
part,  are  too  compHcated  and  obscure  to  permit  at 
present  any  very  accurate  statement  of  their  nature, 
methods,  or  results. 

i6.  The  Efficiency  of  the  Animal  System,  consid- 
ered as  a  heat-engine — a  probably  incorrect  assump- 
tion— is  very  high  as  compared  with  the  machines  of  that 
class  constructed  by  man.  Helmholtz  concluded  from 
the  experiments  of  Hirn  that  the  thermodynamic  efifi- 
ciency  of  the  system  is  about  0.20,  confirming  Hirn's 
own  earlier  deduction  that  it  is  more  efficient  than  the 
steam-engine  as  ordinarily  constructed.  The  fact,  how- 
ever, that  the  body  is  sensibly  uniform  in  temperature 
throughout,  and  that  the  more  work  done  the  more 
rapid  the  circulation,  and  the  more  certain  this  uni- 
formity of  temperature,  seem  to  prove  it  impossible 
that  such  thermodynamic  processes  are  carried  on  in 
the  animal  system  as  are  familiar  to  us  in  our  heat- 
engines,  in  which  the  maximum  possible  efficiency  is 
proportional  to  Carnot's  function — range  of  temperature 
divided  by  maximum  absolute  temperature.  Whatever 
its. method  of  operation,  therefore,  the  animal  machine 
evades  Carnot's  law,  and  must  illustrate  some  as  yet 
undiscovered  process  of  energy-transformation. 

17.  The  Work  of  the  Animal  Machine  is  meas- 
ured in  ''horse-power" — a  rate  equivalent  to  550  foot- 
pounds per  second,  33,000  per  minute,  1,980,000  per 
hour ;  75  kilogrammeters  per  second,  4500  per  minute, 
270,000  per  hour,  in  British  and  metric  measure  respec- 
tively ;  the  latter,  however,  being,  as  will  be  seen  by 
comparison,  one  seventieth  less  than  the  former.  Its 
measure  may  also  be  taken  as  a  days  work,  which  may 
have  widely  different  dynamic  values  in  different  cases. 


THE  ANIMAL  AS  A   MOTOR.  $1 

The  horse,  if  of  average  weight  and  condition,  should  do 
a  day's  work  at  the  rate  of  about  two  thirds  of  a  horse- 
power unit,  or  22,000  to  25,000  foot-pounds  per  minute 
for  the  day.  A  powerful  horse  may  give  a  full  horse- 
power, and  any  animal  may  do  for  a  short  time  vastly 
more  than  its  average  rate  of  work.  A  man  rated  at 
from  a  sixth  to  a  tenth  horse-power  can,  for  a  minute  or 
two  at  a  time,  perform  a  full  horse-power,  or  even  more. 

The  daily  work  of  the  animal,  at  its  best,  depends 
upon  its  exact  accommodation  to  most  favorable  con. 
ditions  for  the  development  of  the  best  work  of  the 
individual,  and  upon  its  size,  natural  strength,  endur- 
ance, and  spirit.  These  qualities  in  turn  are  dependent 
upon  the  breed,  the  state  of  health,  and  the  general 
condition  of  the  animal,  its  food,  its  environment,  the 
weather,  the  climate,  and  the  adaptation  of  its  load  to 
its  habits  and  training.  While  at  work  the  main  ele- 
ments of  most  effective  operation  are  the  load  and  the 
speed  adopted,  at  the  time,  and  its  distribution,  day  by 
day  and  hour  by  hour.  At  maximum  load  the  animal 
does  minimum  work  ;  at  maximum  speed  it  can  carry 
no  load  ;  at  some  intermediate  load  and  speed  it  gives 
maximum  work,  and  this  maximum  varies  with  the  time 
of  working,  day  by  day.  It  is  higher  for  short,  lower 
for  long,  working-days.  For  continuous  work  it  is 
usually  assumed  that  eight  hours  a  day,  at  one  third 
maximum  speed  and  under  one  third  maximum  load, 
gives  highest  results  ;  but  this  is  true  only  under  most 
favorable  conditions,  with  animals  capable  of  doing  a 
full  day's  work,  day  by  day,  continuously  without  loss 
of  strength.  In  many  cases  four  hours,  and  sometimes 
even  one,  constitute  a  fair  day's  work. 

Animal  power  is  most  remarkably  developed  in  the 


52 


THE   ANIMAL  AS  A   MACHINE. 


birds  of  fast  or  of  long  flight.  A  man  can  exert  0.25 
horse-power  for  a  few  minutes  at  a  time,  0.15  horse- 
power by  the  hour — which,  at  1 50  pounds  weight  of  the 
man,  would  require  600  to  about  700  pounds  per  horse- 
power. The  horse  weighs  1500  or  2000  pounds  per 
horse-power  ;  but  the  birds  develop  power  at  the  rate  of 
probably  less  than  one  third  those  figures  for  the  former, 
and  one  eighth  or  one  tenth  for  the  latter.  Falcons  fly 
60  miles  an  hour,  pigeons  35  to  60  for  hours  together, 
and  the  albatross  accompanies  fast  steamers  thousands 
of  miles  without  halt  or  rest.  The  birds  weighing 
probably  lOO  to  200  pounds  per  horse-power  can  carry 
for  a  time  an  added  load  of  30  to  50  per  cent,  as  when 
the  carnivorous  birds  carry  away  their  prey. 

According  to  M.  Fourier,  the  daily  work  of  a  good 
horse  has  a  maximum,  under  the  best  load  for  each 
speed,  at  about  0.90  (2.95  feet)  meters  per  second,  or 
3200  (10.596  feet,  2  miles,  nearly),  an  hour.  Taking 
this  maximum  as  unity,  he  gives  the  following  as  prob- 
able values  of  work  per  pound  at  other  speeds  :  * 


SPEED   PER 

HOUR. 

DAILY  WORK. 

Metres. 

Miles. 

2,000 

1.25 

0.69 

3,200 

2.00 

1. 00 

4,000 

2.50 

•99 

6,000 

375 

•94 

8,000 

5.00 

.83 

10,000 

6.25 

.68 

12,000 

7.50 

•51 

14,000 

8.75 

•33 

16,000 

10.00 

.18 

18,000 

11.25 

.07 

*  Genie  rural,  Herve  Mangon  ;  t.  in.,  p.  175. 


THE  ANIMAL  AS  A   MOTOR,  53 

Where  the  animal  must  develop  maximum  power 
continuously  at  any  considerable  speed,  the  number 
required  for  a  specific  work  will  always  be  greatly  in- 
creased. Thus,  in  coaching,  the  proprietors  of  mail- 
coaches,  even  on  the  admirable  highways  of  Great 
Britain,  maintain  one  horse  per  mile  of  route  for  each 
coach  and  worked  in  fours,  so  that,  going  and  return- 
ing, each  travels  8  miles  per  day,  working  only  an  hour 
or  less  each  day  on  the  average.  The  coach  weighs, 
loaded,  two  tons,  and  its  coefTicient  of  friction  on  good 
roads  is  about  0.035.  Draught-horses  at  2.5  miles  an 
hour  are  expected  to  do  seven  times  the  work  of  coach- 
horses  at  10  miles."^ 

18.  Tabulated  Figures  for  the  work  of  men  and 
animals  follow,  as  given  by  Coulomb,  Navier,  Poncelet, 
Rankine,t  and  others.     Tables  A,  B,  C,  D,  etc. 

According  to  Mr.  Box,  the  work  of  men  and  animals 
may  be  taken,  in  foot-pounds  per  minute,  as : 


-Hours  per  Day. 


F  4                     6                     8                   10 

Man  at  a  winch 220  3,730           3,030          2,640  2,370 

"      ""treadmill 130  5,510          4,490           3,890  3,460 

"      ""capstan 118  4,420           3, 590  3, 100  2,770 

Horse  at  a  capstan.  ...    176  24,780  20,260  17,520  15,670 

Mule     ""         "      180  16,530  13,460  11,680  10,390 

Ox        ""         "      120  22,044  17,980  15,570  13,920 

Ass       ""         "      ....   157  6,060           5,610  4,850  4,320 

The  average  effort  of  a  man  at  a  winch  should  not 
be  assumed  above  15  pounds  for  a  day's  work,  although 
more  than  double  that  figure  may  be  easily  attained 
for  a  brief  period.     From  20  to  30  turns  a  minute  is  a 

*  Barbour's  Cyclopaedia  of  Manufactures. 
\  Steam  Engine,  Chaps.  II.,  III. 


54 


THE  ANIMAL  AS  A   MACHINE, 


A.     WORK   OF  A   MAN.— RANKINE. 


Kind  of  Exertion. 


Raising  his  own  weight  up 
stair  or  ladder 

Hauling  up  weights  with 
rope,  and  lowering  the  rope 
unloaded 


Lifting  weights  by  hand.  ... 
Carrying    weights    upstairs 

and  returning  unloaded 

Shovelling    up     earth    to    a 

height  of  5  ft.  3  in 

Wheeling  earth  in  barrow  up 

slope   of   I    in   12,   \   horiz. 

veloc.  0.9  ft.  per  sec,  and 

returning  unloaded 

Pushing  or   pulling  horizon 

tally  (capstan  or  oar) 


8.  Turning  a  crank  or  winch. 


9.  Working  pump. 
10.  Hammering..  . . 


R 
lbs. 


132- 
26.5 

12-5 

18.0 

\  20.0 

13.2 
15 


V 

ft.  per  sec. 

and  per 

min. 


j    0.5 
I  30.0 

J    0.75 
I  4500 
J  0-55 
I  3300 
jo. 13 
(7-8o 

178^0 


J  0.075 
\  450 
j  2.0 
I  120.0 
5.0  &  300 
2.5  &  150 
14.4  &  864.0 
2.5  &  150.0 
? 


T" 

RV 

3600 
(hours 
p.  day). 

ft.-lbs. 
per  sec. 

and 
per  min. 

8 

J  72.5 
(4550 

6 

]?8oo 

6 

i24.2 

1    1452.0 

6 

\    18.5 
i    IIIO.O 

J7.8 

I  468.0 

10 

3  9-9 
1  594-0 

8 

1", 

(318.0 

? 

62.5:3750 

8 

45;   3700 

2  mins. 

288; 17280 

10 

33;   1980 

8? 

? 

RVT 

ft.-lbs. 

per  day. 


648,000 
522,720 
400,000 
280,800 

356,400 
1,526,400 

1,296,000 

1,188,000 
480,000 


*  Net  weight  of  earth  in  the  barrow. 


B.     PERFORMANCE  OF  A  MAN  IN  TRANSPORTING  LOADS. 


Kind  of  Exertion. 


n.  Walking  unloaded,  transport 
of  own  weight 

12.  Wheeling  load  L  in  2-whld. 

barrow,  return'g  unloaded. 

13.  Ditto  in  i-wh.  barrow,  ditto.. 

14.  Travelling  with  burden 

15.  Carrying    burden,    returning 

unloaded 


16.  Carrying  burden,  for  30  se- 
conds only 


I  V 

L       ft.  per  min, 
lbs.  and 

per  sec. 


224 
132 
90 


252 
126 


j  100 
1i§ 

i2i 
I   150 
J   100 

o  &  702 .  O 
23.i&i38( 


T 

3600 
(hours 
p.  day.) 

LV 
lbs.  con- 
veyed 
I  foot. 

10 

700 

10 

373 

10 

220 

7 

225 

6 

233 

0 

1474.2 

0 

LVT 

lbs. 

conveyed 

I  foot. 


25,200,000 

13,428,000 
7,920.000 
5,670,000 

5,032,800 


THE  ANIMAL  AS  A   MOTOR.  55 

common  range  of  speed,  the  handle  being  15  to  18 
inches  long,  and  about  3500  foot-pounds  per  minute  a 
fair  performance. 

Mr.  D.  K.  Clark  gives  the  following  as  the  work, 
for  one  day,  of  a  laborer,  under  the  specified  condi- 
tions : 


Load. 

Kind. 

Weight. 

Work. 

Carrying  brick .  .  . 

106  lbs. 

600  mile-lbs. 

coal .... 

100   '* 

342     -      " 

Loading  wagon . . 

100    '' 

270     "      " 

boat 

190   '' 

1230     ''      '' 

One  man  breaks  1.5  cubic  yards  of  stone,  or  quarries 
5  to  8  tons  of  rock  per  day. 

The  walking  speed  of  man  is  three  to  four  miles  an 
hour.  Running  eight  miles  an  hour  is  a  common  limit ; 
but  100  miles  in  a  day  for  a  week  together,  and  11^ 
miles  in  one  hour,  have  been  attained  by  practised 
pedestrians.  ''  One  hundred  yards  dash  "  has  been  ac- 
complished at  the  rate  of  20  miles  an  hour.  A  skater 
has  attained  in  one  mile  over  20  miles  an  hour  ;  on  the 
bicycle  about  30  miles  an  hour  has  been  reached  ;  50 
miles  has  been  made  in  2\  hours,  100  miles  in  6  hours, 
388  in  8  hours,  900  in  72.4  hours. ^  Swimming  long  dis- 
tances only  an  average  of  about  one  mile  an  hour  has 
been  made  by  man ;  but  the  porpoise  plays  about  the 
bow  of  ocean  steamers  making  14  and  15  miles  (statute) 
or  more  per  hour. 

Ruhlmann  finds  the  work  done  by  a  Prussian  soldier 
on  the  march,  carrying  64  pounds,  to  be  about  3,000,000 
foot-pounds  per  day.     Various  authorities  give  about 

*  Whiilaker's  Almanach,  1S93. 


56  THE  ANIMAL  AS  A   MACHINE. 

2,000,000  foot-pounds  when  ascending  mountains,  and 
from  1,250,000  to  2,500,000  turning  a  winch. 

It  is  customarily  assumed  that  a  horse  may  develop 
22,500  foot-pounds  per  minute  throughout  a  day's  work 
of  eight  hours ;  will  carry  250  pounds  25  miles  in  a  day 
of  eight  hours;  and  that  1500  pounds,  wagon  included, 
is  a  good  load  for  a  horse  drawing  it  on  good  roads  25 
miles  a  day  of  eight  hours.  The  regular  load  rarely 
exceeds  one  half  the  maximum.  The  load  which  can 
be  raised  by  a  bird  is  said  to  be  about  one  half  its  own 
weight  as  a  maximum. 

Weisbach  states  that  a  man  can  walk,  unloaded,  ten 
hours  a  day  at  3^  miles  an  hour  ;  carrying  80  pounds, 
he  can  walk  seven  hours  at  two  thirds  that  speed.  He 
can  walk  upstairs,  unburdened,  at  the  rate  of  0.48  foot 
per  second,  eight  hours  a  day,  and  performing  1,935,360 
foot-pounds  of  work  per  day,  assuming  his  weight  to 
be  140  pounds.  He  can  traverse,  without  load,  12.5 
times  as  much  space  horizontally  as  vertically.  A  day's 
work  with  a  "  rammer,"  such  as  is  used  by  paviors,  is 
given  as  1,142,400  ft. -lbs.  Turning  a  crank,  man  accom- 
plishes 1,175,040,  with  a  mean  effort  of  16  pounds  and 
a  speed  of  2.4  feet  per  second  during  a  working  day  of 
eight  hours.  On  a  capstan  an  able-bodied  man,  also, 
can  perform  1,382,400  foot-pounds  of  work  per  day. 
On  the  treadmill  he  attains  1,750,000  foot-pounds. 

The  estimates  of  General  Jouffret  yield  the  fol- 
lowing*: *' According  to  the  Guide  JoaimCy  the  ascent 
of  Mont  Blanc,  starting  from  Chamounix,  is  effected  in 
seventeen  hours,  resting-spells  not  included.  The  dif- 
ference of  level  is  3760  metres.     A  person  ascending 

*  Theorie  de  I'Energie  ;  Paris,  1885. 


THE  ANIMAL  AS  A   MOTOR.  5/ 

who  has  a  mean  weight  of  70  kilogrammes  produces, 
then,  in  order  to  rise,  a  work  of  3760  x  70  =  263,000 
kilogrammetres.  This  work  is  borrowed  from  the  heat 
that  the  carbon  and  hydrogon  contained  in  the  food 
eaten  disengage  upon  being  burned  in  the  lungs.  For 
the  sake  of  simplicity,  if  we  reduce  the  entire  energy  to 
a  combustion  of  carbon,  and  recall  that  a  kilogramme 
of  the  latter  furnishes  3,000,000  kilogrammetres,  we  find 
that  the  263,000  kilogrammetres  represented  by  the 
ascent  correspond  to  a  consumption  of  94  grammes  of 
coal — a  consumption  that  should  be  added  to  the 
normal  rations  necessary  for  the  operation  of  the  organs 
during  a  state  of  rest.  Such  consumption  is  8.35 
grammes  per  hour,  or  142  grammes  for  the  seventeen 
hours.  The  total  consumption  of  coal  is  256  grammes, 
representing  708,000  kilogrammetres.  The  perform- 
ance, then,  is 

263,000 


708,000 


=  37  per  cent. 


*'The  performance  of  the  human  machine  drops  to 
21  per  cent  when  we  consider  a  period  of  twenty-four 
hours  composed  of  ten  hours  of  work  and  fourteen  of 
rest,  and  a  mean  daily  work  of  280,000  kilogrammetres. 

'*  The  cannon,  considered  as  a  machine,  is  incompar- 
ably superior  to  a  steam-engine  as  regards  the  time 
necessary  to  produce  a  given  quantity  of  mechanical 
work. 

"  Thus,  for  example,  the  lOO-ton  cannon  develops  in 
one  JmndredtJi  of  a  second  a  quantity  of  work  equal  to 
that  which  would  be  yielded  by  a  47-horse-power  steam- 
engine  in  one  hour.  A  man  of  average  strength  is  still 
lighter  than  an  ordinary  steam  engine  of  equal  power, 


58 


THE  ANIMAL  AS  A   MACHINE. 


but  he  is  much  inferior  to  the  other  animals  of  creation, 
and  particularly  to  insects. 

C.    WORK   OF   A    HORSE   AGAINST   A   KNOWN 
RESISTANCE. 


Kind  of  Exertion. 


Cantering  and  trotting, 
drawing  a  light  railway 
carriage  (thoroughbred) 

Horse  drawing  cart  or 
boat,  walking  (draught- 
horse)  .     

Horse  drawing  a  gin  or 
mill,  walking 

Ditto,  trotting 


{min.  22^  ) 
mean  30J  > 
max.  50    ) 


100 

66 


V 

T 

3600 

RV 

i4i 

4 

447f 

3-6 

8 

432 

3-0 

8 

300 

6.5 

4i 

429 

RVT 


6,444,000 


12,441,600 

8,640,000 
6,950,000 


PERFORMANCE   OF  A    HORSE    IN    TRANSPORTING 
LOADS    HORIZONTALLY. 


Kind  of  Exertion. 

L 

/' 

T 

3600 

L  V 

LVT 

5.  Walking  with  cart,  always  loaded 

6.  Trotting  ditto 

7.  Walking  with  cart,  going  >oaded, 

returning  empty;    V  =  \   mean 
velocity    

1,500 
750 

1,500 

3-6 
7.2 

2.0 
3-6 
7.2 

10^ 

4* 

10 
10 
7 

5i40o 
5,400 

3,000 

972 

1,296 

194,400,000 
87,480,000 

8.  Carrying  burden,  walking 

9.  Ditto,  trotting 

34,992,000 
32,659,200 

The  average  weight  of  a  horse  or  an  ox  may  be 
taken  as  thus : 

Light  carriage-horse  , .  • 800  lbs. 

Heavy  "      1200   '* 

Light  draught-horse 1000   " 

Heavy  "       1600   '* 

Ox 1000    *' 

The  horse  has  galloped  a  mile  in  i  minute  43  sec- 
onds, or  at  the  rate  of  35  miles  an  hour,  and  trotted 
a  mile  in  2  minutes  4  seconds,  or  29  miles  an  hour. 


THE  ANIMAL  AS  A   MOTOR.  59 

An  Austrian  army  officer  rode,  in  June,  1893,  from 
Vienna  to  Berlin,  388  miles,  in  71.33  hours,  or  5.45 
miles  an  hour,  resting  an  hour  in  twelve,  but  losing  his 
horse  after  the  race  was  concluded.  The  ''  cyclists  " 
have  beaten  this  record. 

Rennie  found  the  hauling  power  of  a  draught-horse 
weighing  1200  pounds  was  equal  to  about  108  pounds 
at  2.5  miles  an  hour,  or  22,300  foot-pounds  per  minute, 
for  eight  hours  per  day,  a  20-mile  haul.  This  is  a  little 
over  two  thirds  of  a  Watt  '*  horse-power,"  at  which 
value  Rennie  rates  the  average  draught-horse,  and  this 
is  taken  to  be,  ordinarily,  five  times  the  power  of  a 
man.  Between  2\  and  4  miles  an  hour,  the  hauling 
power  of  the  horse  is  nearly  inversely  as  the  speed. 

The  mule  carries  a  load  of  200  to  400  pounds,  and 
its  day's  work  consists,  usually,  in  the  transportation 
of  the  equivalent  of  5000  to  6000  pounds  one  mile. 
The  ass  carries  175  pounds  and  upward,  and  the  day's 
work  is  the  equivalent  of  3000  to  4000  pounds  one 
mile. 

According  to  Weisbach,  a  horse  should  be  able  to 
carry  240  pounds  on  its  back  3.5  feet  per  second  ten 
hours  a  day.  Carrying  160  pounds  he  should  be  able 
to  trot  7  feet  per  second  seven  hours  a  day,  doing,  in 
the  day,  ten  per  cent  less  work  than  before,  nearly. 

The  pulling  power  is  said  to  be,  as  a  rule,  about  one 
fifth  the  weight  of  the  animal.  Its  usual  effort,  in  the 
case  of  the  horse  at  least,  is  seldom  in  excess  of  one 
tenth,  or  about  one  half  the  maximum.  One  hundred 
pounds  is  a  common  pull  for  the  average  horse  in 
draught  vehicles. 

19.  Effective  Methods  of  Application  of  man-power 
are  sought  by  the  engineer.     The  best  is  considered  to 


6o  THE  ANIMAL  AS  A   MACHINE. 

be  that  of  Coignet  ;  who  arranged  hoists  in  such  man- 
ner that  the  men  employed  would  go  up  ladders  or 
stairs  to  the  summit  of  the  lift  and  then,  by  their 
weight  applied  to  the  "  fall  "  of  the  tackle  used,  de- 
scending to  the  ground  thus  suspended,  the  work  of 
their  descent  would  be  transmitted  to  the  hoist  and 
raise  the  load.  Tables  B,  C,  D,  are  for  common  roads. 
Rankine  gives  as  the  approximate  relative  power  of 
various  animals  the  following :  The  ox  draws  a  load 
about  equal  to  that  of  the  horse,  the  mule  one  half,  the 
ass  one  fourth.  The  ox  moves  at  two  thirds  the  speed  of 
the  horse,  the  mule  the  same  velocity  as  the  horse,  the 
ass  the  same  ;  making  their  respective  working  powers 
as  I  to  f ,  to  \  and  J,  respectively.  In  all  cases,  the 
practical  limit  is  determined  by  the  method  of  applica- 
tion, the  character  of  the  vehicle,  if  any,  used,  and  the 
adjustment  of  the  animal  to  its  surroundings,  as  well 
as  by  its  own  physical  characteristics.  Animals  do 
their  work  mainly  by  draught  of  vehicles.  Its  amount 
depends  largely  upon  the  character  of  the  road 
traversed.  The  effort  required  may  be  taken  as  ap- 
proximately as  follows,  for  total  loads,  including  the 
vehicle  : 

Good  country  road 50  lbs.  per  ton. 

Macadamized  surfaces 40    ''      ''      " 

Asphalt  pavements 38    ''      "      '' 

Wood  ''         35    "      "      '' 

Granite  tramways 27    ''      "      " 

Granite  pavement,  dry,  is  less  likely  to  cause  falls 
than  either  wood  or  asphalt  ;  when  wet,  wood  is  best 
in  this  respect.  Macadamized  and  earth  roads  are  safer 
than  either  of  the  pavements. 


THE  ANIMAL  AS  A   MOTOR.  6 1 

20.  The  Draught  of  Vehicles  is  a  case  of  rolling 
friction."^  Morin,  who  made  very  extended  experi- 
ments, states  its  laws  as  follows  : 

(i)  On  hard  surfaces,  as  paved  and  macadamized 
roads,  the  resistance  is  directly  proportional  to  the 
weight  of  vehicle  and  load,  inversely  proportional  to 
the  diameter  of  wheel,  and  independent  of  the  breadth 
of  wheel-tire.     It  increases  with  velocity. 

(2)  On  soft  ground  the  resistance  increases  inversely 
as  the  breadth  of  tire.  It  does  not  sensibly  vary  with 
velocity.  Morin  concludes,  also,  that  the  line  of  draught 
should  be  horizontal. 

Dupuit,  on  macadamized  roads,  found  the  resistance 
to  vary  nearly  inversely  as  the  square  root  of  the  di- 
ameter of  wheel  and  directly  as  the  load.  He  found 
the  resistance  on  pavements  to  be  increased  at  high 
speeds  by  the  concussions  incident  to  rapid  movement. 
Clark  obtains  a  somewhat  less  simple  law,  which  he  ex- 
presses thus : 

R=:a-\-bv^  yfTu,     .     .     .     .     (i) 

The  work  of  hauling  is  then 

U^Rs^{a^bv-\-  ^/'^i)vt.    .     .     .     (2) 

This  formula  is  deduced  from  the  experiments  of 
Macneil  on  **  metalled  "  roads. f  The  values  of  the 
constants  are,  in  British  measures,  <^  =  30 ;  /^  =:  4  ;  ^  =  10 
pounds  per  ton,  v  being  given  in  miles  per  hour,  /  in 
hours. :t 

*  Friction  and  Lost  work;  Thurston,  p.  84. 
f  Clark's  Manual,  p.  964. 
X  Parnell  on  Roads,  p.  464. 


62  THE  ANIMAL  AS  A   MACHINE. 

The  resistance  of  all  vehicles  on  common  roads  and 
streets  is  principally  resistance  to  rolling,  their  axle- 
friction  being  comparatively  small.  The  work  of  haul- 
ing is,  then, 

U  =  Fs  =  fWs  =  fWvt (3) 

The  draught  of  vehicles  loaded  in  any  stated  manner 
may  be  made  comparatively  easy  or  dif^cult  by  proper 
or  improper  methods  of  attachment  of  the  animal  to 
the  vehicle.* 

The  general  principles  to  be  observed  are  the  fol- 
lowing : 

(i)  In  hauled  loaded  vehicles,  the  Hne  of  traction 
should  be  made  such  as  to  make  the  hauling  power 
dependent  upon  adhesion  between  the  animal  and  the 
ground  equal  to  the  resistance  of  the  vehicle,  with 
some  margin  of  insurance  against  occasional  slipping. 

(2)  The  heavier  the  load,  if  in  excess  of  the  hauling 
power  due  the  animal's  weight,  the  more  should  that 
weight  be  reinforced  by  so  adjusting  the  line  of  trac- 
tion that  it  may  have  a  vertical  component  tending  to 
raise  the  load  and  increase  the  holding  and  hauling 
power  of  the  feet  of  the  animal. 

(3)  With  loads  lighter  than  those  demanding  the 
total  adhesion  due  the  weight  of  the  animal,  the  line 
of  traction  should  be  so  located  that  the  haul,  and,  if 
possible,  the  load  itself,  may  take  off  a  part  of  the 
animal's  weight. 

Thus,  with  a  two-wheeled  vehicle  the  load  may  usu- 
ally be  so  distributed  as  either  to  be  carried,  in  part, 

*  Mr.  T.  H.  Brigg  has  made  a  study  of  this  point,  with  interesting 
results.     Trans.  Am.  Soc.  M.  E  ,  1893. 


THE  ANIMAL  AS  A    MOTOR.  63 

by  the  horse,  or  to  balance  a  part  of  the  weight  of  the 
animal  ;  the  latter  either  carrying  part  and  hauling 
part  of  the  load,  or  hauling  the  load  and,  with  it,  a 
part  of  its  own  weight,  transferred,  by  the  inclined 
upward  line  of  traction,  to  the  load.  The  former  dis- 
position is  obviously  suitable  for  heavy  loads  and  steep 
gradients,  the  latter  for  light  loads  and  level  or  falling 
stretches  of  road.  Heavy  wagons  should  be  handled  in 
such  manner  as  to  give  the  former,  light  carriages  the 
latter,  adjustment.  It  would  probably,  in  the  case  of  the 
heavy  vehicle  be  well  to  provide,  if  practicable,  for  the 
change  of  the  line  of  pull  to  suit  the  load  and  gradient, 
as  has  been  practised  by  Mr.  Brigg  ;  who  finds,  in  some 
cases,  a  loss  of  one  half  the  mechanical  efficiency  at- 
tainable, due  to  inappropriate  methods  of  attachment 
of  the  animal  to  the  vehicle."^     He  concludes  : 

"  The  resistance  which  a  horse  can  overcome  depends 
upon  the  following  conditions  :  (i)  his  own  weight ; 
(2)  his  grip  ;  (3)  his  height  and  length  ;  (4)  direction  of 
trace  ;  (5)  his  muscular  development,  which  determines 
the  power  to  straighten  the  bent  lever  represented  by 
his  body  and  hind  legs  against  the  two  resistances,  the 
vehicle  through  the  trace  attached  to  the  shoulder  and 
the  hind  feet  against  the  ground. 

*'  To  pull  through  a  very  low  trace,  or  to  have  a  man, 
or  even  two  or  three  men,  on  a  horse's  back  is  advisable 
and  even  necessary  if  a  horse  is  expected  to  haul  a 
load  requiring  the  full  force  of  his  muscles  at  any  par- 
ticular moment — and  for  the  moment,  under  such  con- 
ditions, he  would  be  able  to  draw  a  much  greater  load 
than  without  the  added  weight.     But  any  person  can 


Ibid. 


64  THE  ANIMAL  AS  A   MACHINE. 

see  that  the  animal  could  not  travel  far  with  any 
vehicle  if  he  must  carry  three  men  on  his  back  in 
addition  to  hauling  his  load." 

"  Therefore,  to  deal  justly  with  our  horses,  we  should 
not  only  study  cause  and  effect,  but  should  devise  some 
means  by  which,  automatically,  every  possible  advan- 
tage could  be  given  to  the  horse  at  all  times.*  Other- 
wise there  must  be  a  constant  waste  of  energy,  tiring 
the  horse  prematurely  and  increasing  the  chances  of 
his  stumbling  and  falling." 

These  principles  are  thus  illustrated  by  Mr.  Brigg : 

In  the  accompanying  figure,  let  the  horse  be  har- 
nessed in  the  usual  manner  and  driven  up  hill. 

Suppose  that  the  horse  is  exerting  a  force  of  36  lbs. 
through  AB  in  a  line  from  the  hame  to  the  centre  of 
the  wheel.  Let  AC  represent  the  vertical  depression 
necessary  to  hold  down  the  shafts.  Since  AB  and  AC 
are  the  forces  necessary  to  produce  motion,  by  com- 
pleting the  parallelogram  ACDB  we  find  that  AD 
represents  the  resultant  of  the  forces  AC  and  AB. 
Thus  we  determine  one  arm  of  the  lever,  GS,  acting 
against  GT,  the  other  arm.  GS  is  a  line  drawn  at  right 
angles  from  the  resolved  angle  of  force  AD. 

If  the  load  had  been  balanced  on  the  axle,  then, 
regardless  of  the  angle  of  trace  or  hame-chain,  the 
angle  of  draught  would  be  through  AB  to  the  centre 
of  the  wheel.  Then  a  line  at  right  angles  with  AB  to  G 
would  have  been  the  short  arm  of  the  lever,  which  would 
have  enabled  the  horse  to  have  pulled  a  much  greater 
load  than  is  possible  with  the  longer  arm,  GS.     But, 


*  Mr.  Brigg  had  already  devised  and  applied  such  a  system  of  self- 
adjustment  of  the  harness  as  to  secure  this  effect. 


THE  ANIMAL  AS  A    MOTOR. 


65 


the  load  being  behind  the  axle,  the  forward  weight 
of  the  animal  is  reduced  by  the  lift  of  the  shafts  at  A, 
and  the  result  is  the  same  as  if  the  traces  had  been 
put  up  at  the  point  D,  and  the  load,  with  a  33-lb.  pull 
through  such  a  trace,  would  be  exactly  balanced. 

Let  UV  represent  the  horizon  passing  through  the 
point   D.     If  DA    represents  33   lbs.,   then   FA   will 


Vendh-fgio  pulfffie  Horse\ 
~  n  G  off  the  Ground 


Resultant  of  Components  A  B  and  A  C  as  A  D,  or  N D  added 
to  Horse's  Weight,  N  D  equals  U  taken  from  the  Load 
and  Carried  by  the  Horse, 


Fig.  I  . — Haulage  of  Vehicles. 

represent  4  lbs.,  so  that  4  lbs.  must  be  added  to  the 
horse's  natural  weight  by  the  pull  AD.  Or,  if  the  pull 
through  the  trace  AB  is  36  lbs.,  then,  drawing  BE 
parallel  wdth  the  horizon  UV,  EA  (14  lbs.)  will  repre- 
sent the  depression  due  to  a  36-lb.  pull  through  AB. 
But  when  the  lift  due  to  the  shafts,  10  lbs.,  is  deducted 
from  the  depression  of  14  lbs.,  there  remains  as  before 
an  increased  weight  of  4  lbs.  on  the  horse. 

When  the  horse  is  pulling  with  the  same  force  upon 
a  level,  as  in  Fig.  2,  we  find  very  different  results. 
Let  PA  be  the  direction  from  the  hames  to  the  centre 


66 


THE  ANIMAL   AS  A   MACHINE. 


of  the  wheel  and  representing  a  36-lb.  pull.  The  load 
having  been  moved  farther  to  the  rear,  the  lift  at  the 
belly-band  is  still  10  lbs.  2X  P — the  load  is  moved  back- 
ward to  shift  the  centre  of  gravity.  The  resultant  of 
the  two  components  PA  and  PB  is  PC,  and  PC  now 
equals  about  35.9  lbs.,  whereas  the  resultant  AD  in 
Fig.  6  is  only  33  lbs.,  or  2.9  lbs.  less  than  on  the  level. 
It  will  now  be  found  that  36  lbs.  pull  through  PA  will 
increase  the  horse's  weight  4.5  lbs.,  represented  by 
PO,  which  is  determined  by  drawing  AO  from  A 
parallel  with  the  horizon,  cutting  the  Hne  of  gravity  PE, 


X   """^----.-.^.s^ 


Fig.  2. — Haulage  of  Vehicles. 

But,  as  the  disposition  of  the  load  is  such  that  10  lbs. 
are  taken  from  the  horse,  it  is  obvious  that,  if  only  4.5 
lbs.  are  put  back  by  the  stated  pull  of  36  lbs.,  the  horse 
has  still  5.5  lbs.  less  than  his  natural  weight  in  Fig.  2, 
while  in  Fig.  i  he  has  4  lbs.  more  than  his  natural 
weight. 


THE  ANIMAL  AS  A    MOTOR. 


67 


If  the  load  be  shifted  to  the  front  end  of  the  cart, 
as  indicated  in  Fig.  3,  the  resultant  of  the  forces  PJ 
and  PK  hes  in  the  direction  of  PL,  and  the  added 


Fig,  3. — Haulage  of  Vehicles. 

weight  on  the  horse  is  22  lbs.  instead  of  4  lbs.  as  in 
Fig.  I,  tending  to  thrust  his  hind  foot  into  the  ground 
at  O,  and  he  is  able  to  pull  40  lbs.  as  against  33  lbs. 
under  the  conditions  indicated  in  Fig.  i. 

It  will  be  observed  in  Fig.  i  that  the  point  of  appli- 
cation of  force  A  (the  hame)  is  above  the  horizontal 
line  UV,  drawn  through  the  point  D,  this  being  the 
point  at  which  the  traces  might  be  fixed  with  an 
advantage  equal  to  having  them  attached  to  the  axle 
when  the  given  lift  is  exerted  at  A,  with  a  lift  at  the 
belly-band  as  set  forth  ;  whereas  P,  the  point  of  appli- 


68  THE  ANIMAL  AS  A   MACHINE. 

cation  of  force  in  Fig.  2,  is  now  much  below  the  hori- 
zontal line  MN,  drawn  through  the  point  C  on  the 
resultant,  or  virtual  line  of  draught.  Comparing  the 
triangles  ABE  (Fig.  i)  and  PAO  (Fig.  2),  AB  and 
PA  represent  the  pull  through  the  traces,  and,  al- 
though the  force  is  the  same — 36  lbs.,  the  result  is 
different. 

If  AB  in  Fig.  i  represents  a  36-lb.  pull,  and  AC  "d. 
lO-lb.  lift,  then  AD  (33  lbs.)  is  the  resultant  direction 
of  force  appHed  by  the  animal.  A  36-lb.  pull  through 
AB,  together  with  a  lift  of  10  lbs.  through  AC  ox  2. 
pull  of  33  lbs.  through  AD,  will  both  be  effective  in 
lifting  2.6  lbs.  from  the  horse's  fore  quarters.* 

Thus  the  animal  may  be  very  effectively  aided,  or 
may  be  totally  incapacitated  by  good  or  bad  adjust- 
ment of  the  line  of  traction.  In  all  cases  this  Hne 
should  be  given  such  incHnation  as  will  insure  increased 
pressure  of  the  animal  upon  the  ground  for  heavy  pull- 
ing, and  decrease  its  weight  in  the  opposite  case,  just 
to  the  extent  required  to  make  adhesion  ample  with- 
out unnecessary  surplus. 

21.  Muscular  Power  varies  enormously  with  the 
animal,  its  condition,  habits  of  exercise,  and  other  cir- 
cumstances ;  but  the  results  of  many  experiments  indi- 
cate that  the  muscles  of  the  human  body  have  a  power 
measured,  in  good  condition,  by  a  maximum  of  not 
far  from  10  kilogrammes  per  square  centimetre,  and 
averaging  7  or  8  (142,110,114  pounds  per  square  inch 
respectively).  The  influence  of  exercise  and  custom 
on  the  working  power  of  the  muscle  is  enormous,  in 
some  cases  being  found  to  vary  in  the  proportion  of 


Ibid. 


THE  ANIMAL  AS  A   MOTOR.  69 

one  to  at  least  three. ^  This  quantity  of  work  done 
has  no  ascertained  relation  to  the  value  of  the  energy 
of  the  foods  consumed  ;  although  the  work  which  an 
animal  can  do  is  dependent  upon  the  quantity  of  energy- 
producing  food  which  it  can  digest  and  assimilate  under 
the  conditions  to  which  it  is  subjected  while  at  work. 
The  stored  energy  of  the  foods  varies,  according  to 
Frankland,  from  about  500  kilogrammes  per  gramme,  or 
45  foot-pounds  per  ounce,  for  lean  meats,  to  three  times 
this  quantity  for  the  grain-foods  and  to  six  times  this 
value  for  butter;  but  the  total  need  of  the  system 
determines  the  kind  and  quality  of  food  desirable  at 
any  given  time  and  for  any  given  case.  In  general 
the  use  of  the  grain-foods  is,  from  a  scientific  and 
possibly  from  a  physiological  point  of  view,  most 
productive  of  useful  power  in  both  man  and  the 
domestic  animals.  Where  the  work  is  severe  and  long- 
continued  no  time  is  allowed  for  proper  digestion  and 
assimilation,  and  in  such  cases  special  care  must  be  taken 
to  provide  the  best  conditions  for  insuring  endurance. 
It  is  in  illustration  of  this  point  that  the  case  of  the  Arab 
living  on  the  coffee-berry,  and  the  pedestrian  on  long 
walks  living  entirely  on  the  same  material  in  the  form 
of  a  beverage,  may  be  referred  to.  The  warm  drink  is 
at  once  stimulus  and  food,  and  demands  little  energy 
in  digestion  and  assimilation.  A  permanent  dietary, 
however,  must  contain  all  the  elements  demanded  for 
nutrition  of  all  parts  of  the  system  in  proper  propor- 
tions, and  must  at  the  same  time  provide  the  needed 
mechanical  and  other  stimuli  of  all  the  organs  of  the 
body.     The  ivJiole  wheat  used  by  man,  fruits,  and  the 

*  Nipher  on  Strength  of  the  Muscle,  Am.  Jour.  SlL,  Nov.  1875. 


JO  THE  ANIMAL   AS  A    MACHINE. 

grains  consumed  by  horses  and  cattle  are  considered 
to  be  most  perfect  examples  of  these  foods.  Eggs  and 
milk,  among  animal  foods,  correspond  most  nearly  to 
the  same  desirable  composition,  but  require  an  admix- 
ture of  vegetable  foods  to  insure  their  proper  action  in 
the  human  system.  The  meats  are  always  defective 
in  essential  elements  of  food,  and  can  never  be  safely 
used  alone  by  man.  The  carnivora,  devouring  the 
whole  body  of  their  prey,  and  especially  fond  of  the 
blood,  which  contains  all  its  elements  in  solution,  are 
able  thus  to  live  upon  animal  food. 

Working  animals  are  always  herbivorous  or  grami- 
nivorous, and,  as  in  the  case  of  man,  should  have  their 
best  dietary  carefully  determined  to  insure  their  effi- 
cient action  as  prime  movers,  and  maximum  economy 
of  transformation  of  the  potential  energy  of  their 
foods  into  mechanical  power.  When  doing  no  work 
an  herbivorous  diet  is  probably  best ;  but  when  work- 
ing the  grains,  and  when  hard  worked  "cut  feed  "  and 
coarse  meals,  mixed  with  a  moderate  amount  of  water 
and  given  warm,  are  best.  Cold  water  should  be  avoided 
with  meals,  and  when  the  creature  is  warm  from  exer- 
tion especially  ;  but  oat-meal  water  can  be  safely  taken 
in  any  quantity  by  man  or  beast. 

22.  The  Uses  of  Foods  in  the  body  are  thus  stated 
by  Professor  Atwater^ : 

Food  furnishes  : 

(i;  The  material  of  which  the  body  is  made. 

(2)  The  material  to  repair  the  wastes  of  the  body,  and  to  protect 
its  tissues  from  being  unduly  consumed. 

Food  is  consutned  as  fuel  in  the  body  to  : 

(3)  Produce  heat  to  keep  it  warm. 

*  Century  Magazine,  July  1887,  P-  370. 


THE  ANIMAL  AS  A   MOTOR.  7 1 

(4)  Produce  muscular  and  intellectual  energy  for  the  work  it  has  to 
do. 

The  body  is  built  up  and  its  wastes  are  repaired  by  the  nutrients. 

The  nutrients  also  serve  as  fuel  to  warm  the  body  and  supply  it  with 

strength. 

[forms  the  nitrogenous  basis  of  blood,  muscle, 

^,  .       ,  r      .    I       sinew,  bone,  skin,  etc. 

The  protein  of  food  A  .     ,  ,  .        ,  ,       ,1., 

*^  IS  changed  mto  fats  and  carbohydrates. 

\^is  consumed  for  fuel. 

^,      ,  ^      r  r     J  \  *^^^  stored  in  the  body  as  fat. 

The  fats  of  food  \  ,  ,  -^ 

(  are  consumed  for  fuel. 

The  carbohydrates     j  are  changed  into  fat. 

of  food  {  are  consumed  for  fuel. 

^,         .         ,  (  are   transformed  into  the  mineral  matters    of 

The  mmeral  matters  )      ,  j      t.       • 

\       bone  and  other  tissue, 
of  food  \  ,  .  .  ^, 

(  are  used  m  various  other  ways. 

A  growing  child  or  young  animal  requires  much 
muscle  and  nerve-making  material,  and  the  proportions 
of  the  several  elements  in  the  food  are  more  nearly 
those  of  the  body  itself  than  in  the  case  of  the  adult. 
The  adult,  when  doing  little  work,  requires  little  food, 
and  that  mainly  of  the  kinds  which  are  required  to 
supply  heat  and  to  compensate  the  slight  wastes  of 
tissue  then  occurring  ;  while  the  working  system,  and 
particularly  if  hard  worked,  demands  considerable 
quantities  of  combustible,  heat-producing  food.  Simi- 
lar differences  of  dietary  are  required,  as  the  climate 
compels  the  development  of  more  or  less  of  caloric  to 
preserve  the  temperature  of  the  body,  which  at  above 
104"  Fahr.,  or  a  little  below  98",  fails  to  meet  the 
requirements  of  life. 

According  to  Dr.  Letheby,  the  working-power  of  the 
human  body  may  be  taken  as  follows  * : 

*  Letheby  on  Food,  p.  96. 


72 


THE  ANIMAL  AS  A   MACHINE. 


Foot-pounds. 
External  work  or  actual  labor..    i,oi  1,670 

Work  of  circulation  (75  beats  a  minute). . . .       500,040 

Work  of  respiration  (15  a  minute) 98,496 

Total  ascertainable  work  per  day 1,610,206 

The  ascertainable  external  and  internal  work  of  the 
food  we  eat  is  only  one  sixth  of  its  actual  energy,  ac- 
cording to  Letheby ;  but  it  is  not  impossible  that  the 
unascertained  work  of  the  vascular  system  and  other 
parts  may  account  for  the  full  amount,  nearly. 

According  to  Dr.  Frankland,  this  power  is  supplied 
by  food  in  the  following  proportions  ^ : 

ENERGY-VALUES    OF    FOODS. 


Per  Cent 

of 
Water 
in  Ma- 
terial. 

Pounds  of  Water 
Raised  i°  F. 

Pounds  Lifted  i 
Foot  High. 

Name  of  Food. 

When 

Burnt 

in 

Oxygen. 

When 

Oxidized 

in  the 

Body. 

When 

Burnt 

in 

Oxygen. 

When 

Oxidized 

in  the 

Body. 

Butter 

15 
24 
15 
15 
15 
13 
47 
19 
62 

44 
54 
71 
71 

71 
73 

87 
86 
89 

18.68 

11.95 

10.30 

10.12 

10  12 

9.80 

8.82 

8.61 

6.13 

5-74 
5-09 
4.60 
3-38 
3.38 
2.60 
1.70 
1.36 
1. 12 

18.68 
11.20 
10.10 
9.87 
9-57 
9-52 
8.50 
8.61 
5.86 
5-52 
4.30 
4.14 
3-01 
3.01 
2.56 
1.64 
1.33 
1.08 

14-421 
9.225 
7-952 
7.813 
7-813 
7.566 
6.809 
6.649 
4-732 
4-431 
3.929 
3-551 
2.609 
2.609 
2.007 
1.312 
I-050 
.864 

14.421 
8.649 
7.800 
7-623 
7-487 
7.454 
6.559 
6.649 
4.526 
4.263 
3.321 
3.200 
2.324 
2.324 
1.987 
1.246 
1. 031 
.834 

Cheese 

Oatmeal 

Wheat  flour 

Ground  rice 

Yolk  of  efifsf 

Lump  sugar 

Entire  t^g  (boiled). . 
Bread 

Ham 

Mackerel. 

Lean  beef 

Lean  veal 

Potatoes 

Milk 

Carrots 

Cabbage 

*  Frankland  on  Food  of  Man,  1887,  p.  68. 


THE  ANIMAL  AS  A   MOTOR. 


73 


23.  Dietaries. — Dr.  Pavy  gives  the  following  as  the 
quantities  of  the  specified  foods^required  to  support 
human  Hfe  * : 


Nitrogen , 300  grains. 

Carbon 4800     " 

Carbon.       Nitrogen. 

14,000  grains  (2  lbs.)  of  bread  contain 4200  140 

5,500      "      (about  I  lb.)  of  meat  contain 605  165 

Total  (2f  lbs.) 4805  305 

Six  pounds  meat \  4^°°  S""^^"^  c^^^^"' 

(  1309       "      nitrogen. 

Four  pounds  bread \  9°°°  ^'^'""^  ^^'^b^"- 

(    300       "      nitrogen. 

The  estimates  of  Moleschott  for  weight  of  foods  in  a 
dry  state,  for  the  average  individual,  are  as  follow  :  f 


Dry  Food. 


Albuminous  matter 

Fatty  matter 

Carbohydrates 

Salts 

Total 


In  Oz. 

Avoir. 


4.587 

2.964 

14.250 

1.058 


22.859 


In  Grains. 


2006 

1296 

6234 

462 


9998 


In  Grammes. 


130 

84 

404 

30 


648 


Reckoning  ordinary  food  to  contain  50fi^  of  water,  then,  these  23 
ounces  will  correspond  to  46  ounces  solid  food  in  the  condition  eaten 
— additional  to  this,  60  to  80  ounces  of  water  is  taken  in  some  form. 
The  dynamic  or  force-producing  value  of  this  daily  standard  diet 
amounts  to  about  4000  foot-tons. 

The  relative  values  of  the  common  articles  of  diet 
are  given  by  Scammell  as  follows  \  : 


*  Treatise  on  Food,  p.  473. 

t  Ibid.,  p.  452.     Also  Mott's  Chart  (N.  Y.,  J.  Wiley  &  Sons,  1889). 

X  Mott's  Chemist's  Manual,  p.  575. 


74  THE  ANIMAL  AS  A   MACHINE, 

THE    RELATIVE   VALUES   OF    FOODS. 


Articles. 


Wheat 

Barley 

Oats 

Northern  corn. , 
Southern  "  . 
Buckwheat. . . . 

Rye 

Beans 

Peas 

Rice 

Potatoes 

Parsnips 

Turnips 

Cabbage 

Milk 

Veal 

Beef...    

Lamb 

Mutton 

Pork    

Chicken 

Codfish 

Trout 

Salmon 

Oysters 

Eggs  (white  of) 
"      (yolk  of). 

Butter 

Bacon 

Cheese 

Chocolate 

Cream 

Ham 

Lard 

Onions 

Barley 


As 

Material 

for  the 

Muscles. 

As 

Heat- 
givers. 

14.6 

66.4 

12.8 

52.1 

17.0 

50.8 

12.3 

67.5 

34.6 

39-2 

8.6 

530 

6.5 

75.2 

24.0 

40.0 

23.4 

41.0 

5.1 

82.0 

1.4 

15.8 

2.1 

14.5 

1.2 

4.0 

1.2 

6.2 

5-0 

8.0 

17.7 

14-3 

19.0 

14.0 

19.6 

14-3 

21.0 

14.0 

17-5 

16.0 

21.6 

1.9 

16.5 

I.O 

16.9 

0.8 

20.0 

Some  fat 

12.6 

13.0 

.... 

16.9 

29.8 

*  8'.4 

100. 0 
62.5 

30.8 

28.0 

8.8 

3-5 

35-0 

88.0 

4-5 
32.0 

.... 

lOO.O 

0.5 

5-2 

4-7 

78.0 

As  Food 

for  the 

Brain  and 

Nervous 
System. 


1.6 

4.2 
3.0 
I.I 
4.1 
1.8 
0.5 
3  5 
2.5 
0.5 
0.9 
1.0 

0.5 
0.8 
1.0 

2.3 
2.0 
2.2 
2.0 
2.2 
2.8 
2.5 
4-3 
6  or  7 
0.2 
2.8 
2.0 

0.5 
4.7 
1.8 

4.4 

0.5 
0.2 


Water, 


14  o 
14.0 
13.6 
14.0 
14  o 
14.2 

13-5 
14.8 
14. 1 
9.0 
74.8 
794 
90.4 

91-3 
86.0 

65.7 
65.0 

63.9 
63.0 

64.3 

73-7 
80.0 
78.0 
74.0 
87.2 
84.2 
51.3 

28'.  6 
36.5 

92.0 
28.6 

93-8 
9-5 


Waste. 


3.4 
16.9 
16.9 

5.1 

8.1 
22.4 

4.3 
17.7 
19.0 

3-4 
7.1 
3.0 
3-9 
0.5 


1-4 


7.6 


The  study  of  these  figures  permits  the  construction 
of  a  proper  dietary  for  any  case  in  which  stated 
rations  are  required  or  desirable.  Professor  Atwater 
gives  the  following"^  : 

*  Century  Magazine,  185S,  p.  25S. 


THE  ANIMAL  AS  A    MOTOR. 


75 


STANDARDS   FOR   DAILY   DIETARIES.* 

Weights  of  Nutrients  and  Calories  of  Energy  (Heat  Units) 
IN  Nutrients  required  in  Food  per  Day. 


1.  Children  to  ij^  years \ 

2.  Children  2  to  6  years \ 

3.  Children  6  to  15  years \ 

4.  Aged  woman 

5.  Aged  man 

6.  Woman    at    moderate    work  j 

(Voit) f 

7.  Man  at  moderate  work  (Voit). 

8.  Man  at  hard  work  (Voit) 

9.  Man  with  moderate  exercise  I 

Playfair) f 

10.  Active  labor  (Playfair) 

11.  Hard  labor  (Playfair) 

12.  Woman  with    light    exercise  I 

(Writer) f 

13.  Man      with     light     exercise  ( 

(Writer) ( 

14.  Man    at    moderate    work        | 

(Writer) \ 

15.  Man  at  hard  work  (Writer) 


Nutrients. 

Poten- 

Protein. 

Fats. 

Carbo- 
hydrates. 

Total. 

tial 
Energy. 

Grms. 

Grms. 

Grms. 

Grms. 

Calories. 

28 
(20-36) 

(36-70) 

37 

(30-45) 

40 

(35-48) 

75 

(60-90) 

200 

(100-250) 

140 

295 

767 
1418 

(70-80) 
80 
100 

(37-50) 
50 
68 

(250-400) 
260 

350 

443 

390 
518 

2041 

1859 
2477 

92 

44 

400 

536 

2426 

118 
145 

56 
100 

500 
450 

674 
695 

3055 
3370 

119 

51 

531 

701 

3139 

X 

71 
71 

568 
568 

795 
824 

3629 
3748 

80 

80 

300 

460 

2300 

100 

100 

360 

560 

2820 

125 

125 

450 

700 

3520 

150 

150 

500 

800 

4060 

DIETARIES    FOR    MAN    DOING    MODERATE    MUSCULAR 

V^ORK. 


Nutrients. 

Potential 

Protein. 

Fats. 

Carbo- 
hydrates. 

Energy. 

Playfair   

119  grms. 
130      " 

120  " 
118      " 

51  grms. 
40     " 

35     " 
56     " 

530  grms. 
550      " 
540      " 
500      " 

3135  calories 
3160       " 
3032       " 
3055 

Moleschott 

Wolff 

Voit 

Mr.  Edward  Atkinson  has  given  a  number  of  die- 
taries, each  having  the  requisite  proportion  of  proteids, 

*  Nos.  I,  3,  4,  and  5  are  as  proposed  by  Voit  and  his  followers  ol 
the  Munich  School  ;  No.  2  by  Atwater.  One  ounce  =  2'^\  grammes, 
nearly. 


1^ 


THE  ANIMAL  AS  A   MACHINE. 


Starch,  and  fat  for  thorough  nutrition  with  minimum 
consumption  of  food  and  at  minimum  cost.  Of  these 
the  following  is  an  example  of  a  dietary  which  would 
serve  where  low  wages  or  other  conditions  compel  the 
adoption  of  most  economical  rations  : 
LOW-COST  DIETARY.* 
Proteid.     Fat. 


Article.        Pounds, 

Flour 22 

Grain 12 

Butter 2 

Suet 2 

Sugar 2 

Potatoes 10 

Beets 

Carrots 

Onions 

Squash 

Cabbage 

Parsnips        J 


2.64 

1.68 

.02 


.20 


.44 

.84 

1.73 

1.78 


Carbo- 
hydrate. 

15.18 

7.60 


1-93 
2.10 


Calories.    Cost  at  Bos- 
ton prices  1891 

0.55 


13   .03 


50 


36,520 
19,800 
7,230 
7,200 
3,600 
4,300 


120 


57        4.67  4.82    27.31 

1.90      .155  .160     .910 

Variables  in  Table  Showing  Method  of  Analysis 
Beef,  neck  or 

I2C".S^)2.00  .40 

5  -62  .34 

4  .40  2.80 

2  .40  .10 

I  .19  -03 

I  .03  .78 


For  30  days. 
For  I  day.. . 


shin 

Mutton,  neck. 

Bacon 

Beef-liver.  . . . 

Veal 

Salt  Pork.... 


79,770 
2,659 


5,200 
2,476 
11,840 
1,120 
460 
3,160 


.48 
.56 
.12 
.10 
.25 


.25 


$2.31 
.077 


.72 
.30 
.48 
.12 
.08 
.08 


For  30  days. .     25 


3.64     4-45 


Total. 


82 


For  I  day. . . .  2.73 


.277 


9.27 
.309 


27.31 
.910 


24,256 

104,026 
3,467.5 


.78 


$4.09 
.136 


The  succeeding  dietary  is  one  which  is  considered 
an  economical  and  satisfactory  scheme  for  families  of 

*  The  prices  on  which  these  computations  are  made  were  the  retail 
prices  in  Boston,  Mass.,  U.  S.  A.,  in  the  first  six  months  of  the  year 
1891. 


THE  ANIMAL  AS  A    MOTOR.  7/ 

small  income.  In  both  cases  the  first  list  will  sustain 
life,  and  the  second  comprises  the  usually  added  but 
unessential  articles.  In  acting  as  commissary  the  en- 
gineer should  endeavor  always  to  provide  the  equiva- 
lent of  the  first  dietary,  and,  where  practicable,  the 
second. 


22 

3 

Articles. 

pounds  Flour, 
"        Oatmeal, 

at 
at 

|0.02^ 
.04 

$0.55 
.12 

\^cllUIlCS. 

3 

"        Cornmeal, 

at 

.03 

.09 

6 
2 

"        Hominy, 
"        Butter, 

at 

at 

.04i 

.28 

.27 
.56 

2 

Suet, 

at 

.06 

.12 

lO 

"        Potatoes, 

at 

.02^ 

.25 

3 

2 

"        Cabbages, 
"        Carrots, 

at 
at 

.03 

.02| 

.09 
•05 

2 

"        Onions, 

at 

.o5i 

.11 

2 
2 

Sugar, 
-  57 

Variables, 
pounds  shin  of  Beef, 

"        round  of  Beef, 

at 

at 
at 

.05 

$0.06 

.18 

.10 

$2.31 

$0.36 
.36 

79»770 

6 

"        neck  of  Mutton, 

at 

.06 

.36 

2 

I 

Eggs, 
"        Cheese, 

at 

at 

.18  doz.    .27 
.16            .16 

30 

Skimmed  Milk, 

at 

.02 

.60 

I 

White  Beans, 

at 

.07 

.07 

I 

Pease, 

at 

.07 

.07 

4 

2 

"        Halibut,  nape, 
Haddock, 

at 
at 

.05 
.08 

.20 
.16 

3 

"        Salt  Cod, 

at 

.08 

.24 

I 

2 

"        Oleomargarine, 
"        Macaroni, 

at 
at 

.16 
.15 

.16 
.30 

I 
2 

"        Oatmeal, 
Cornmeal, 

at 
at 

.04 
.03 

.04 
.06 

I 

Rice, 

at 

.06 

.06 

I 

"        Hominy, 
-66 

at 

.04 

.04 

$3-51 

41,051 

123  pounds,  total  for  30  days 

4.1      "         "       "      I  day. 

Cost  per 

week 

,  $1-35. 

$5.82 
.194 

120,821 
4.027 

78  THE  AiYIMAL   AS  A   MACHINE 

24.  The  ''Mechanism   of  Transmission"  of  the 

power  of  the  animal  is  the  vehicle  or  other  apparatus 
through  which  the  power  is  exerted  in  the  moving  of 
the  load.  In  some  cases  the  load  is  directly  applied,  as 
where  pack-animals  are  employed ;  in  others  a  wagon 
is  used ;  in  still  other  cases  the  pull  on  a  rope  is  made 
effective  in  raising  weights.  A  strong  man  can  walk 
an  average  of  about  3^^  miles  an  hour  10  hours  a  day, 
unloaded  ;  under  80  pounds  he  can  walk  at  half  this 
speed  seven  or  eight  hours  a  day ;  and  he  may  lift  at 
long  intervals  180  to  200  pounds.  The  work  of  hori- 
zontal transport  may  be  approximately  computed  by 
taking  it  at  0.08  the  product  of  weight  carried  into 
distance  moved  over.  Thus  measured,  we  find  from 
the  above  statement  that  a  man  should  do  about 
2,000,000  foot-pounds  of  work  per  day,  his  weight 
being  included  in  the  amount  taken  as  load.  By  the 
use  of  a  wagon,  or  its  equivalent,  the  weights  that  may 
be  transported  are  increased,  often,  ten  times  or  more. 
Training  may  double  the  efficiency  of  a  workman  in 
manual  employments  and  enormously  increase  it  in 
cases  of  skill  coming  of  long  practice.  The  differences 
between  reputably  first-class  workmen  may  amount  to 
15  or  20  per  cent. 

The  pull  of  the  average  draught-animal  is  usually 
not  far  from  one  fifth  its  weight.  Gerstner  gives  us 
the  following"^  : 

Weight.    Av.  Pull.    Fft.  per   Work  per      Work  per 
Lbs.  Lbs.        Sec.  Av.        Sec.  8-hr.  Day. 

Man 150  30  2.5  75  2,160,000 

Horse...  600  120  4.0  480  13,824,000 

Ox 600  120  2.5  300  8,640,000 

Mule 500  100  3.5  350  10,080,000 

Ass 360  72  2.5  180  5,184,000 

*  Mechanik,  vol.  i. 


THE   ANIMAL   AS  A    MOTOR.  79 

25.  Equations  connecting  the  time,  effort,  and  work 
of  animals  have  been  proposed,  all  of  which  are  only- 
approximate,  at  best  ;  since  the  conditions  of  each 
case  are  certain  to  differ  more  or  less  from  the  mean, 
and  are  always  difficult  to  evaluate.  Rankine  follows 
Maschek,  who  gives  the  expression 

^      _F      r  _ 

i?,  +  F,  "f"  r,  ~  ^ ' 

in  which  i?, ,  F, ,  T^,  are  respectively  one  third,  each, 
of  the  maximum  load,  maximum  speed,  and  maximum 
time  in  the  day's  work.  Thus  a  maximum  day's  work 
is  obtained  under  the  load  R  —  R^,  at  the  speed 
F=  F, ,  and  T^^T^,  working  eight  hours  per  day. 
Any  departure  from  this  adjustment  is  presumed  to 
give  sensible  loss  of  result.  Bouguer  proposes  and 
Gerstner  endorses  the  following,  R^  and  V^  being  max- 
imum loads  and  speeds : 

^ = (-  vY' 

Gerstner,  taking  R^  and  V,  at  their  mean  values,  as 
per  table,  would  write  the  equations  thus  : 

For  small  variations  from  the  times,  loads,  and  speeds 
of  best  effect,  the  total  effect  may  be  taken  as  varying 
with  those  variations. 

In  ascending  inclines,  the  work  may  be  taken  as 
approximately  increasing  with  the  inclination  and  at 
a  rate  proportional  to  the  ratio  i  -[- {a  -^  \  1.5°) ;  since 


8o 


THE   ANIMAL  AS  A   MACHINE. 


the  work  performed  in  horizontal  carriage  of  burdens 
is  nearly  equivalent   to   raising  the  total  weight  one 
foot  in  five,  for  which  we  have  sin-i-i-:^  11.5°.     Xhe 
art  of  securing  best  results  in  the  use  of  animals  draw- 
mg  loads  in  vehicles  of  various  sorts  is  that  of  so  pro- 
portioning  load,  line    of   pull,  weight  of  vehicle,  and 
speed  of  travel  as  to  permit  the  animal  to  take  its 
natural   gait   and    best  total    effort    under   load,  this 
effort  being  measured  at  the  traces.     Obviously,  the 
lighter  the  wagon  or  cart  it  is  found  practicable  to  em- 
ploy for  the  proposed  load  the  better.    Also,  the  larger 
the  loads  transported  in  one  vehicle  the  better,  as  a 
rule  ;  and  thus,  in  all  large  operations,  heavy  loads  in 
comparatively  light  carriages,  and  drawn  by  numbers 
of  animals,  give  most  economical  results.     As  inclines 
decrease   the    useful  work   in    rapid   proportion  with 
their  rise,  the  production  of  level  and  smooth  roads  is 
an   essential   to   economy.     This  is  illustrated  in  the 
case  of  railways,  where  enormous  sums  are  expended 
to  insure  straight,  level,  and  smooth  tracks.     For  men 
the  treadmill,  and  for  animals  well-constructed  '^  horse- 
powers," embodying  the  same  principles  of  construc- 
tion, give  highest  efficiency  as  measured  by  the  work 
performed  per  day,  in  foot-pounds  or  kilogrammetres. 
Walking   up   a   moderate    incline    carrying   only  the 
weight  of  the  body  is  the  most  easy  and  natural  of  all 
methods    of   employing   its   power.       This   system    is 
capable,  however,  of  but  very  limited  appHcation  in 
ordmary  industrial  work.      It  is  oftenest  seen  in  use  in 
threshing-machines  and  other  agricultural  apparatus. 

26.  In  Selection  and  Care  in  the  employment  of 
men  and  animals,  the  engineer  is  compelled  to  regard 
them  as  machines,  to  be  selected  with  careful  reference 


THE   ANIMAL   AS  A   MOTOR.  8 1 

to  the  exact  requirements  of  the  work  proposed  to  be 
done,  to  be  handled  in  such  manner  as  to  give  him 
maximum  returns  for  his  expenditures,  and  to  be  made 
to  produce  large  commercial  results  throughout  the 
period  of  their  use.  Fortunately,  a  wise  regard  of 
these  principles  results  in  giving  the  man  or  the  animal 
highest  health,  in  insuring  him  against  overwork,  and 
in  encouraging  high  spirits  by  the  supply  of  good  food, 
permitting  ample  allowance  for  sleep  and  rest,  and 
prolonging  the  period  of  useful  life.  In  exceptional 
cases  the  animal  machine  must  be  exposed  to  deleteri- 
ous influences,  overstrain,  or  liability  to  serious  acci- 
dent ;  but  these  cases  can  usually  be  made  extremely 
rare  by  intelligent  engineering,  and,  in  the  case  of 
man  at  least,  the  individual  so  exposed  receives  what 
is  thought  by  him  satisfactory  compensation  for  the 
risks  so  taken. 

In  the  selection  of  the  man  or  animal  for  a  specified 
work,  the  wise  and  experienced  engineer,  or  his  con- 
tractor, looks  for  light,  active,  spirited  creatures  for 
light  work,  heavy  and  powerful,  though  slow,  animals 
for  heavy  work,  and  can  usually  find  just  that  com- 
bination of  qualities  of  body,  intelligence,  and  spirit 
which  his  experience  teaches  him  are  best  for  the 
specified  purpose.  The  racehorse,  the  roadster,  the 
hackney,  and  the  draught-animal  all  have  their  special 
parts  to  perform.  Neither  can  satisfactorily  do  the 
work  of  the  other  ;  and  the  same  is  true  of  man, 
whether  performing  purely  manual  labor,  working  at  a 
trade,  or  taxing  his  mind  in  the  direction  of  an  indus- 
trial army  or  otherwise.  For  every  sort  of  task  there 
is  to  be  found  a  kind  of  man  specially  and  peculiarly 
adapted  to  its  successful  accomplishment.     Not  only 


82  THE  ANIMAL   AS  A    MACHINE. 

individuals,  but  families,  tribes,  and  even  races,  adapt 
themselves,  through  natural  constitution  and  peculiar 
characteristics  of  body  and  mind,  to  special  kinds  of 
work.  Among  the  best  species,  races,  tribes,  or 
families,  individuals  may  always  be  found  especially 
well  fitted  to  perform  a  specified  work ;  and  among 
such  individuals,  the  age,  state  of  health,  conditions  of 
environment,  may  produce  serious  differences  at 
different  times.  All  such  variations  are  noted  by  the 
engineer  and  serve  as  the  basis  of  his  judgment  in 
apportioning  work,  in  assigning  duties,  and  in  deter- 
mining compensation. 

The  work  once  assigned,  the  person  in  charge 
should  be  expected  not  only  to  see  that  the  conditions 
of  best  effect  are  adhered  to,  strictly  and  continuously, 
but  to  arrange  the  times  and  methods  of  serving 
meals,  the  character,  amount,  and  method  of  prepara- 
tion of  the  dietary  with  a  view  to  insuring  the  best 
possible  conversion  of  its  potential  energy  into  work 
and  at  minimum  cost  consistent  with  highest  results. 
Even  satisfaction  with  the  bill-of-fare,  by  promoting 
appetite  and  digestion,  is  an  element  of  success,  with 
animals  as  well  as  with  men.  Periods  of  rest  should 
be  so  arranged  that  the  food  may  be  taken  neither 
when  fatigue  nor  immediately  succeeding  labor  may  in- 
terfere with  its  digestion.  Two  meals,  even  one  hearty 
and  well-digested  meal  per  day  is  sometimes  found, 
for  this  reason,  better,  on  the  whole,  than  a  larger 
number  resulting  in  impaired  digestion  and  defective 
nutrition.  In  hot  climates,  particularly,  natives  are 
observed  often  to  be  well  satisfied  with  a  single  meal, 
taken  after  a  hard  day's  work  ;  the  precaution  being 
observed    to  secure  an  hour  of    complete  rest  before 


THE  ANIMAL   AS  A   MOTOR,  83 

taking  it.  Hard-worked  stage-horses,  fed  an  hour  be- 
fore going  upon  the  road  in  the  morning  with  a  warm 
mixture  of  cut  hay  and  corn-meal,  moderately  wet, 
and  fed  again  after  their  rest  on  coming  in  at  night, 
have  been  found  to  do  the  season's  work  better  than 
when  given  a  third  meal  at  noon.  The  meal  should, 
in  all  cases,  consist  of  nutritious  food  of  proper  com- 
position, and  in  ample  quantity  to  satisfy  the  appetite, 
without  permitting  excess. 

No  less  essential  in  securing  the  most  that  can  be 
obtained  from  the  working  man  or  animal  is  the  pro- 
vision of  suitable  clothing  and  housing.  Weather- 
tight,  warm,  thoroughly  comfortable,  and  yet  well- 
ventilated  stables  are  essential  to  highest  economy  in 
the  employment  of  animals  ;  and  the  same  care,  pre- 
cisely, is  demanded  in  providing  for  men,  with  the 
additional  requirement  that  everything  within  reason 
that  shall  conduce  to  content  and  cheerfulness,  high 
spirits,  ambition,  and  an  inclination  to  do  their  best 
work  should  be  conscientiously  provided. 


III. 

FINAL   DEDUCTIONS.* 

27.  Our  Progress,  whether  in  the  direction  of  indus- 
trial improvement  or  of  intellectual  growth,  depend, 
the  first  mainly,  the  second  largely,  upon  the  extent 
and  the  success  of  man's  utilization  of  the  four  great 
natural  forces,  or  *' energies,"  as  the  man  of  science 
calls  them  :  heat,  light,  electricity,  mechanical  or  dyna- 
mic power.  Civilization  is  based  upon  their  application 
to  the  purposes  of  humanity  in  the  world  of  matter; 
intellectual  and  even  moral  progress  is  advanced  by 
that  steady  march  of  improvement  which,  in  modern 
times  especially,  has  so  constantly  promoted  the  ma- 
terial welfare  of  the  world,  and  has  thus  given  leisure 
for  that  employment  of  the  mind  in  higher  work  which 
is  the  essential  prerequisite  to  either  intellectual  or 
moral  elevation. 

The  greatest  of  all  our  problems  to-day  is  thus  that 
of  making  this  utilization  of  the  forces  of  nature  more 
general,  more  efficient,  and  more  fruitful.  Could  the 
engineer,  to  whom  all  this  work  is  intrusted,  find  a  way 
of  producing  steam-power  at  a  fraction  its  present 
cost ;  could  he  transform  heat  energy  directly  and 
without  waste  into  dynamic  ;  could  he  find  a  method 
of  evolution  of  light  without  that  enormous  loss  now 

*  From  The  Forum,  Sept.  1892  :  "  The  Great  Problems  of  Science," 
by  R.  H.  Thurston. 

84 


FINAL  DEDUCTIONS.  85 

inevitable  in  the  form  of  accompanying  heat ;  could 
he  directly  produce  electricity,  without  other  and  lost 
energy,  from  the  combustion  of  fuel — could  he  do 
these  things  to-day,  the  growth  of  all  that  is  desirable 
to  mankind  and  the  advancement  of  all  the  interests 
and  powers  of  the  race  would  be  inconceivably  ac- 
celerated. Moral  sentiments,  logical  power,  inventive 
genius,  capacity  for  accomplishing  all  the  grander  tasks 
of  civiHzation,  develop  together.  All  gain  and  retain 
existence  through  the  mysterious  power,  possessed  by 
all,  of  transforming  and  utilizing  those  original  natural 
energies  coming  to  us  all  alike  from  the  central  sun, 
and  to  the  central  sun  from  initial  chaos  and  a  diffused 
universe.  Every  motion  and  every  power  of  each  and 
all  is  due  to  conversion  of  these  primary  energies  for 
a  specific  purpose  and  in  a  specific  manner. 

The  engineer,  to  whom  is  confided  this  duty  of 
utilizing  all  the  forces  of  nature  for  the  benefit  of  his 
fellows,  has,  however,  now  apparently  reached  a  point 
beyond  which  he  can  see  but  little  opportunity  for 
further  improvement,  except  by  slow  and  toilsome  and 
continually  limited  progress.  He  seems  to  have  come 
very  nearly  to  the  limit  of  his  advance  in  the  directions 
which  have,  up  to  the  moment,  been  so  fruitful  of 
result.  His  steam-engine  is  doing  nearly  the  best  that 
can  be  done,  so  far  as  he  can  see,  in  the  conversion 
of  heat  into  power ;  light  is  produced  through  the 
steam-engine  and  the  dynamo-electric  machine  about 
as  efficiently  as  he  can  hope  to  obtain  it  by  known 
methods;  heat  is  obtainable  for  his  thousand  purposes, 
economically  at  least,  only  by  the  combustion  of  his 
rapidly  disappearing  stores  of  fuel  laid  by  in  the  past 
millenniums  for  his  use  during  a  brief  life  on  the  globe, 


86  THE  ANIMAL  AS  A    MACHINE. 

and  without  visible  substitute  when  they  shall  have 
been  exhausted ;  and  civilization,  the  life  of  the  race, 
dependent  upon  our  coal-beds,  is  only  assured  of 
ultimate  and,  on  the  geologist's  scale  of  time,  early 
extinction  ;  unless,  indeed,  again  consulting  nature 
and  studying  the  lessons  of  life,  as  we  have  so  often 
profitably  done  before,  we  can  learn  of  new  ways  of 
availing  ourselves  of  existing  forms  of  energy  in 
nature,  or  of  enormously  improving  our  methods  and 
reducing  those  wastes  which  are  now  so  frightful,  as 
judged  from  the  standpoint  of  both  the  engineer  and 
the  man  of  science.  Whether  we  can  expect  or  even 
hope  to  accomplish  the  first  of  these  tasks  is  extremely 
doubtful,  not  to  say  absolutely  improbable ;  that  we 
may  possibly  succeed  in  the  second  may  be  less  un- 
likely. In  any  case,  our  only  recourse  is  the  same 
method  which  has  brought  us  all  that  we  now  possess : 
scientific  research  and  the  study  of  nature's  own 
methods. 

28.  What  we  are  to  Seek  is,  first,  a  method  of 
producing,  directly  or  by  modification  of  other  ether- 
vibrations,  just  that  sort  of  ether -wave  which  we 
require,  in  the  form  of  heat,  light,  or  electricity,  of 
exactly  defined  rate  and  amplitude  of  vibration  ; 
secondly,  the  complete  transformation  of  either  or  all 
forms  into  mechanical  power,  into  ''  dynamic  "  energy. 
It  is  easy  to  say  and  usually  is  safe  to  assert  that  what 
has  been  done  may  be  again  done ;  what  is  accom- 
plished to-day  in  nature  may  be,  in  a  similar  manner 
or  by  parallel  methods,  performed  by  man.  Nature 
accomplishes  many  of  the  tasks  that  man  is  about 
attempting,  and  has  been  holding  up  to  him  the 
solution  of  his  problems  throughout  the  ages.     It  is 


FINAL   DEDUCTIONS.  87 

for  him  to  solve  her  riddles  and  thus  to  obtain  power 
at  a  fraction  of  its  present  cost ;  prolong  the  life  of 
the  race  indefinitely ;  secure  light,  isolated  from  heat, 
and  in  many  times  the  quantity  for  a  given  amount  of 
labor  now  expended ;  and  produce  electricity  without 
loss  and  directly,  instead  of,  as  at  present,  through  the 
intervention  of  heat-engines  with  their  now  enormous 
wastes.  Human  progress  depends  upon  the  ability  of 
mankind  to  do  more  work,  and  to  accomplish  greater 
tasks,  to  supply  the  necessaries  of  life  with  less  expen- 
diture of  time  and  strength,  thus  to  secure  leisure  for 
the  production  of  the  comforts  and  the  luxuries  that 
give  modern  society  its  characteristics,  and  to  insure 
that  leisure  for  thought,  invention,  intellectual  de- 
velopment of  every  kind,  which  still  more  strikingly 
characterize  the  highest  civilization.  In  all  this,  only 
the  application  of  the  forces  of  nature  without  waste 
and  the  complete  subjection  of  all  its  energies  can 
give  maximum  result. 

It  is  now  well  known  that  the  heat-engines,  whether 
steam,  gas,  hot  air,  or  ether,  only  utilize  a  fraction  of 
the  power  latent  in  their  fuel,  and  that  this  fraction, 
as  a  maximum,  in  even  an  ideally  perfect  engine,  is 
measured  by  the  division  of  the  range  of  temperature 
through  which  they  expand  their  '*  working  fluids  "  by 
the  "  absolute  "  temperature  of  the  fluid  as  supplied 
to  the  engine ;  that  is,  a  temperature  measured  from 
a  point  about  460°,  on  the  Fahrenheit  scale,  below  the 
Fahrenheit  zero.  This  fraction,  we  have  learned,  is, 
in  the  case  of  the  modern  steam-engine,  usually 
between  one  fourth  and  one  half ;  while  the  actual 
performance  of  our  engines  falls  to  one  fourth  or  one 
half   this   ideal   maximum,  in   the   ordinary   and    best 


««  THE  ANIMAL  AS  A    MACHINE. 

engines,  respectively.*  The  engine  fully  utilizing, 
ideally,  but  two  and  one  half  pounds  of  steam  and 
one  fourth  of  a  pound  of  coal  per  horse-power  per 
hour  practically  demands  six  to  eight  times  this 
amount,  even  when  of  the  best  construction  ;  while 
the  average  engine  probably  utilizes  but  one  pound  in 
ten,  and  often  but  one  in  twenty,  wasting  from  ninety 
to  ninety-five  per  cent  of  all  the  heat  from  its  furnaces. 
The  gas-engine  gives  higher  thermodynamic  perform- 
ance than  the  steam-engine ;  but  it  compensates  this 
advantage  by  loss,  through  a  ''water-jacket,"  of  one- 
half  of  all  the  heat  that  it  should  completely  transform 
into  useful  work.f  No  method  is  yet  discovered 
of  imitating  nature  in  direct  conversion  of  heat 
into  other  forms  of  energy  without  waste ;  and  our 
production  of  light,  in  our  most  recent  and  most 
wonderful  inventions,  involves  the  same  waste  by  the 
intermediate  use  of  the  heat-engine  for  primary  trans- 
formation of  heat  into  mechanical  energy,  in  turn  to 
be  converted,  with  great  efficiency,  into  electricity, 
thence  to  be  once  more  transformed,  with  great  waste 
again,  into  light.  The  direct  evolution  of  light, 
purely,  or  of  electricity  alone  and  without  loss,  from 
fuel  oxidation,  though  it  is  constantly  performed  by 
nature,  is  as  yet  beyond  the  power  of  man.  Could 
these  problems  of  life  be  solved,  power  and  light 
would  cost  us  but  a  small  fraction  of  their  cost  to-day ; 
and  the  exhaustion  of  our  coal-beds  would  be  deferred 

*"  Steam  and  its  Rivals,"  R.  H.  Thurston:  Forum,  May  1888, 
p.  34T.  Also  "Manual  of  the  Steam-engine,"  vol.  i.  (New  York, 
J.  V^iley  &  Sons,  1890). 

f  "  Last  Days  of  the  Steam-engine,"  R.  H.  Thurston:  North 
American  Review^  July  1889. 


FINAL  DEDUCTIONS.  89 

thousands  of  years.  Were  grander  problems  ever 
presented  or  nobler  prizes  ever  offered  the  man  of 
science  than  these  ?  Nature  solved  them  in  the 
earliest  days  of  the  earth's  history ;  it  begins  to  seem 
probable  that  man  may  find  a  way  to  penetrate  the 
secrets  and  solve  the  problems  of  life  and  vitality. 
All  that  he  seeks  may  be  evolved  from  the  mysteries 
and  lessons  of  life. 

29.  The  Living  Body  is  a  machine  in  which  the 
"law  of  Carnot,"  which  asserts  the  necessity  of  waste  in 
all  thermodynamic  processes  and  in  every  heat-engine, 
and  which  shows  that  waste  to  be  the  greater  as  the  range 
of  temperature  worked  through  by  the  machine  is  the 
more  restricted,  is  evaded  ;  it  produces  electricity  with- 
out intermediate  conversions  and  losses ;  it  obtains 
heat  without  high-temperature  combustion,  and  even, 
in  some  cases,  light  without  any  sensible  heat.  In  other 
words,  in  the  vital  system  of  man  and  of  the  lower 
animals  nature  shows  us  the  practicability  of  directly 
converting  any  one  form  of  energy  into  any  other, 
without  those  losses  and  unavoidable  wastes  character- 
istic of  the  methods  the  invention  of  which  has  been 
the  pride  and  the  boast  of  man.  Every  living  creature, 
man  and  worm  alike,  shows  him  that  his  great  task  is 
but  half  accomplished  ;  that  his  grandest  inventions  are 
but  crudest  and  remote  imitations ;  that  his  best  work 
is  wasteful  and  awkward.  Every  animate  creature  is  a 
machine  of  enormously  higher  efficiency  as  a  dynamic 
engine  than  his  most  elaborate  construction  as  illus- 
trated in  the  30,000  horse-power  engines  of  the  "  Cam- 
pania" or  the  ''  Lucania,"  or  in  the  most  powerful 
locomotive.  Every  gymnotus  living  in  the  mud  of  a 
tropical  stream  puts  to  shame  man's  best  effort  in  the 


90  THE   ANIMAL   AS  A    MACHINE. 

production  of  electricity ;  and  the  minute  insect  that 
flashes  across  his  lawn  on  a  summer  evening,  or  the 
worm  that  lights  his  path  in  the  garden,  exhibits  a  sys- 
tem of  illumination  incomparably  superior  to  his  most 
perfect  electric  lights. 

Nature  in  each  of  these  cases  converts  the  energy  of 
chemical  union,  probably  of  low-temperature  oxidation, 
into  just  that  form  of  energy,  whether  mechanical  or  of 
a  certain  exactly  defined  and  required  rate  of  ether- 
vibration,  that  is  best  suited  to  the  intended  purpose, 
and  without  waste  in  other  force,  utilizing  even  the 
used-up  tissue  of  muscle  and  nerve  for  the  production 
of  the  warmth  required  to  retain  the  marvellous  ma- 
chine at  the  temperature  of  best  efficiency,  whatever 
the  environment,  and  exhaling  the  rejected  resultant 
carbonic-acid  gas  at  the  same  low  temperature.  Here 
is  nature's  challenge  to  man  !  Man  wastes  one  fourth 
of  all  the  heat  of  his  fuel  as  utilized  in  his  steam-boiler, 
and  often  ninety  per  cent  as  used  in  his  open  fire- 
places ;  nature,  in  the  animal  system,  utilizes  substan- 
tially all.  He  produces  light  by  candle,  oil-lamp,  or 
electricity,  but  submits  to  a  loss  of  from  one  fifth  to 
more  than  nine  tenths  of  all  his  stock  of  available 
energy  as  heat ;  she,  in  the  glowworm  and  firefly,  pro- 
duces a  lovelier  light  without  waste  measurable  by  our 
most  delicate  instruments.  He  throws  aside  as  loss 
nine  tenths  of  his  potential  energy  when  attempting  to 
develop  mechanical  power ;  she  is  vastly  more  econom- 
ical. But  in  all  cases  her  methods  are  radically  different 
from  his,  though  they  are  as  yet  obscure.  Nature  con- 
verts available  forms  of  energy  into  precisely  those  other 
forms  which  are  needed  for  her  purposes,  in  exactly  the 
right  quantity,  and  never  wastes,  as  does  invariably  the 


FINAL   DEDUCTIONS,  9 1 

engineer,  a  large  part  of  the  initial  stock  by  the  pro- 
duction of  energies  that  she  does  not  want  and  cannot 
utilize.  She  goes  directly  to  her  goal.  Why  should 
not  man  ?     He  has  but  to  imitate  her  processes. 

Mysterious  as  seem  these  processes  and  methods, 
however,  and  wonderful  as  seem  their  results  when 
compared  with  the  crude  ways  of  the  engineer  and 
the  man  of  science,  we  at  least  know  something  of 
them,  and  are  even  familiar  with  many  facts  relating  to 
them.  The  facts  are  these :  Every  living  creature 
throughout  the  animal  kingdom  is  a  machine  which 
takes  into  its  internal  furnace,  or  whatever  it  may 
prove  to  be,  its  fuel,  its  "  food,"  composed  of  vegetable 
matter  or,  like  the  body  receiving  it,  itself  directly  de- 
rived from  vegetation  ;  and  by  a  chemical  process  in 
what  the  chemist  calls  the  "  wet  way  "  it  consumes  this 
food,  the  resulting  products  of  this  chemical  action  being 
such  as,  dissolved  in  the  blood,  may  be  converted  into 
brain,  nerve,  muscle,  and  fat ;  and  by  later  combustion 
and  transformations  at  low  temperature  it  may  produce 
heat  certainly,  electricity  probably,  often  light,  and 
always  mechanical  power.  The  composition  of  this 
fuel  is  known  to  be  principally  familiar  chemical  ele- 
ments mingled  with  the  rarer  in  minute  proportions. 
The  hydrocarbons,  water,  and  a  little  lime,  phosphorus, 
sulphur,  and  other  minerals,  such  as  iron,  constitute 
the  food  of  all  living  creatures. 

Every  process  involved  is  carried  on  at  '' blood-lieat  " 
in  the  higher  animals,  and  at  much  lower  temperatures 
in  the  "■  cold-blooded  "  creatures  ;  and  all  parts  of  the 
system  are  retained  at  substantially  the  same  tempera- 
ture at  all  times.  All  heat  is  thus  the  result  of  low- 
temperature  combustion  ;  all  light  and  electricity  are 


92  THE  ANIMAL   AS  A    MACHINE. 

evolved  at  a  constant  low  point  on  the  scale,  and  these 
energies  are  converted  into  new  forms,  or  into  dynamic 
energy,  and  applied  to  the  performance  of  work  with- 
out variation  of  that  temperature.  That  heat  is  pro- 
duced is  a  matter  of  constant  experience  and  observa- 
tion, and  we  throw  off  more  as  we  work  harder,  whether 
with  mind  or  body,  and  as  we  move  more  rapidly. 
That  this  heat,  so  far  as  converted  into  other  energies 
by  the  body,  must  be  so  converted  at  a  sensibly  con- 
stant temperature  is  obvious  from  the  fact  that  the 
change  goes  on  in  a  mass  of  circulating  fluids ;  that 
this  proves  that  the  conversion  is  not  thermodynamic, 
but  is  due  to  some  entirely  different  and  unknown 
method,  is  equally  evident  to  the  engineer,  who  under- 
stands that  only  so  could  the  "law  of  Carnot "  be 
evaded.  That  this  action  is  possibly  electrodynamic  is 
indicated  by  the  fact  that  electric  currents  traverse  the 
system,  and  that  we  may  at  any  moment  compel  the 
muscles  to  do  work  by  the  application  of  a  current 
from  an  external  source. 

30.  Of  the  Methods  of  Production  of  Energies 
in  the  body,  we  know  as  yet  absolutely  nothing ;  but 
we  do  know  that  electricity  may  be  produced  in  large 
quantity,  and  at  ''  high  pressure,"  as  the  electrician 
says,  as  illustrated  by  the  torpedo  and  the  gymnotus 
or  electric  eel ;  and  the  anatomist  knows  the  mechani- 
cal structure  of  the  organs  from  which  it  is  evolved, 
though  he  is  ignorant  of  the  processes  therein  con- 
ducted. We  also  know  that  the  best  currents  for 
electrodynamic  operations  are  those  of  low  intensity, 
such  as  are  easiest  of  control  and  insulation  in  the 
body.  By  analogy  with  the  other  methods  of  trans- 
formation, we   may  presume  that  the  source   of  this 


FINAL   DEDUCTIONS.  93 

vital  fluid  in  the  animal  is  low-temperature  combustion 
or  other  chemical  action,  and  that  a  system  of  direct 
conversion  is  there  in  operation. 

Scientific  men  are  somewhat  more  familiar  with  the 
case  of  the  firefly,  curiously  enough  ;  that  is  to  say, 
the  production  of  light  without  heat,  as  well  as  the 
transformation  of  energies  resulting  in  the  economical 
production  of  heat  and  power  in  the  animal  system. 
It  has  long  been  known  that  certain  chemical  com- 
pounds, notably  fats  containing  sulphur  and  phospho- 
rus, may  be  burned  at  exceedingly  low  temperatures, 
with  an  evolution  of  a  mild  light  almost  or  quite 
entirely  free  from  heat.  Some  such  compounds  are 
found  in  nature,  and  the  chemist  has  artificially  pro- 
duced others.  He  finds  that  he  may  at  will  produce, 
in  some  cases,  slow  and  cold  light-production  or  rapid 
and  heat-producing  oxidation.  Numerous  experiments 
upon  the  firefly  and  the  glowworm  indicate  that  theirs 
is  a  light  thus  obtained.  This  so-called  "■  phosphores- 
cence" is  seen  in  many  insects,  worms,  fishes,  and 
mollusks,  and  even  in  vegetable  and  mineral  matter. 
For  a  century  this  investigation  has  been  in  progress, 
and  it  is  well  established  that  the  low-temperature 
combustion  of  a  peculiar  substance,  given  form  in  the 
body  of  the  firefly,  for  instance,  by  peculiar  organs 
specially  constituted  for  that  purpose,  results  in  the 
production  of  light  without  heat.  This  has  been  most 
recently  and  most  conclusively  proved  by  Messrs. 
Langley  and  Very,  who  show  by  actual  measurement 
with  the  Langley  "  bolometer,"  an  instrument  capable 
of  measuring  even  the  heat  received  from  the  moon, 
that  "  insect  light  "  is  accompanied  by  approximately 
one  four-hundredth  part  of  the  heat  which  is  ordinarily 


94  THE  ANIMAL   AS  A    MACHINE. 

associated  with  the  radiation  of  flame  of  the  luminous 
quality  of  those  familiar  to  all  of  us.  Thus  '*  nature 
produces  this  cheapest  light  at  about  one  four-hundredth 
part  of  the  cost  of  the  energy  which  is  expended  in  the 
candle-flame  and  at  but  an  insignificant  fraction  of  the 
electric  light  or  the  most  economic  light  which  has  yet 
been  devised."  Many  deep-sea  fishes  and  nnmberless 
animalcules  exhibit  a  solution  of  this  problem. 

31.  The  Advantage  to  be  hoped  for  from  the  sub- 
stitution of  the  economical  ways  of  nature  for  the 
wasteful  ways  of  man  may  be  imagined  from  the  fol- 
lowing facts:  Experiments  by  Mr.  Merritt,  in  the  Cor- 
nell University  laboratories,  have  shown  the  wastes  of 
the  incandescent  electric  lamp  to  be  from  93I-  to  99I- 
per  cent,  according  to  intensity  of  current ;  while  Mr. 
Nakano's  tests,  in  the  same  place,  of  the  arc  lamp  give 
a  waste  of  95  to  84  per  cent.  The  insect  wastes  almost 
nothing.  But  even  now  the  electric  light  has  ten  or 
fifteen  times  the  efficiency  of  the  oil-lamp,  and  is  still 
better  as  compared  with  the  candle.  Professor  Lang- 
ley  found  the  common  gas-burner  to  waste  99  per  cent 
of  the  developed  energy  of  combustion.  His  fireflies 
were  more  efficient  in  the  proportion  of  one  to  thousands. 
The  six  millions  of  tons  of  coal  supposed  to  be  con- 
cealed in  the  earth,  at  our  present  rate  of  consumption, 
if  employed  for  power-production,  would  supply  about 
fifteen  thousand  millions  of  horse-power  for  twelve 
thousand  years ;  but  could  we  discover  and  employ 
nature's  methods  and  gain  in  such  proportion  as  is 
indicated  above,  we  might  feel  sure  that  all  the  wants 
of  the  race  would  be  supplied  as  long  as  the  earth 
should  continue  the  possible  abode  of  man.  Years 
ago  it  was  remarked  in  an  inaugural  address  as  presi- 


FINAL  DEDUCTIONS.  95 

dent    of   the    ''  American  Society  of    Mechanical   En- 
gineers "  *: 

"  I  have  sometimes  said  that  the  world  is  waiting  for 
the  appearance  of  three  great  inventors,  yet  unknown, 
for  whom  it  has  in  store  honors  and  emoluments  far 
exceeding  all  ever  yet  accorded  to  any  one  of  their 
predecessors.  The  first  is  the  man  who  is  to  show 
how,  by  the  consumption  of  coal,  we  may  directly  pro- 
duce electricity,  and  thus,  perhaps,  evade  that  now 
inevitable  and  enormous  loss  that  comes  of  the  utiHza- 
tion  of  energy  in  all  heat-engines  driven  by  substances 
of  variable  volume.  Our  electrical  engineers  have  this 
great  step  still  to  take,  and  are  apparently  not  likely 
soon  to  gain  the  prize  that  will  reward  some  genius  yet 
to  be  born.  The  second  of  these  greatest  of  inventors 
is  he  who  will  teach  us  the  source  of  the  beautiful  soft- 
beaming  light  of  the  firefly  and  the  glowworm,  and 
will  show  us  how  to  produce  this  singular  illuminant 
and  to  apply  it  with  success  practically  and  commer- 
cially. This  wonderful  light,  free  from  heat  and  from 
consequent  loss  of  energy,  is  nature's  substitute  for  the 
crude  and  extravagantly  wasteful  lights  of  which  we 
have,  through  so  many  years,  been  foolishly  boasting. 
The  dynamo-electrical  engineer  has  nearly  solved  this 
problem.  Let  us  hope  that  it  may  be  soon  fully  solved, 
and  by  one  of  those  among  our  own  colleagues  who  are 
now  so  earnestly  working  in  this  field,  and  that  we  may 
all  live  to  see  him  steal  the  glowworm's  light  and  to  see 
the  approaching  days  of  Vril  predicted  so  long  ago  by 
Lord  Lytton.  The  third  great  genius  is  the  man  who 
is  to  fulfil  Erasmus  Darwin's  prophecy  closing  the 
stanza : 

*  Transactions  "A.  S.  M.  E.,"  November  1881,  R.  H.  T. 


96  THE   ANIMAL   AS  A    MACHINE. 

"  '  Soon  shall  thy  arm,  unconquered  steam,  afar 
Drag  the  slow  barge  or  drive  the  rapid  car, 
Or  on  wide-waving  wings  expanded  bear 
The  flying  chariot  through  the  fields  of  air  '  " 

And  even  this  latest  of  the  mechanic's  triumphs,  al- 
ready known  to  present  far  less  difficulty  than  was 
formerly  supposed,  will  attain  highest  success  only 
when  nature's  methods  of  energy-transformation  are 
discovered  and  adopted. 

Should  the  day  ever  come  when  transformations  of 
energy  shall  be  made  in  nature's  order,  and  when 
thermo-electric  changes  shall  be  a  primary  step  toward 
electrodynamic  application  to  purposes  now  universally 
attained  only  by  the  unsatisfactory  processes  of  thermo- 
dynamics as  illustrated  in  our  wasteful  heat-engines, 
the  engineer,  following  in  his  work  the  practice  of 
nature,  which  has  been  so  successful  throughout  the 
life  of  the  animal  kingdom,  will  find  it  easy  to  drive 
his  ship  across  the  ocean  in  three  days ;  will  readily 
concentrate  in  the  space  now  occupied  by  the  engines 
of  the  "  Majestic  "  a  quarter  of  a  million  horse-power; 
will  transfer  the  3,000,000  horse-power  of  Niagara  to 
New  York,  Boston,  Philadelphia,  to  be  distributed  to 
the  mills,  shops,  houses,  for  every  possible  use,  furnish- 
ing heat,  light,  and  power  wherever  needed  ;  and  may 
possibly  do  quite  as  much  for  the  benefit  of  mankind 
by  breaking  up  the  modern  factory  system  and  distrib- 
uting labor  in  comfortable  quarters  as  by  this  reduc- 
tion of  costs  of  products  to  the  consumer.  One  of  the 
many  difficulties  in  the  way  of  successful  navigation  of 
the  air  is  known  to  be  that  of  securing  some  propelling 
instrument  that  shall  not  weigh  more  than  about  ten 
pounds  to  the  horse-power.     Could  we  evade  Carnot's 


FINAL   DEDUCTIONS.  97 

law  by  complete  energy-transformation,  we  could  to- 
day build  engines  of  over  400  horse-power  to  the  ton 
weight,  and  that  obstacle  would  be  out  of  our  way. 
Could  we  completely  transform  heat  or  mechanical 
power  into  light,  a  resulting  advantage  would  also  be 
the  reduction  of  the  whole  system  of  light-producing 
machinery  in  weight  and  bulk  in  corresponding  degree. 
These  gains  would  be  observed  in  innumerable  direc- 
tions. 

32.  Costs. — On  the  other  hand,  nature  in  all  her 
transformations  makes  use  of  chemical  processes  and 
organic  and  complex  compounds  that  may  prove  to  be 
too  costly  as  substitutes  for  the  fuels,  though  the  latter 
are  subject  to  present  wastes ;  and  thus  the  question 
of  dollars  and  cents,  always  controlling,  comes  in  to 
confuse  the  wisest  of  scientific  men.  However  that 
may  be,  these  problems  must  always  afford  instructive 
lessons  to  the  student  of  the  mysteries  of  nature  ;  and 
the  bare  possibility  that  by  following  her  methods  he 
may  find  ways  of  so  enormously  benefiting  his  fellow- 
man  and  of  adding  so  greatly  to  the  comfort,  the 
pleasure,  the  safety,  and  the  opportunities  of  the  race, 
must  be  quite  sufficient  to  stimulate  every  young 
aspirant  for  fame  and  every  lover  of  research  to  strive 
to  achieve  some  one  or  all  of  these  solutions  of  the 
grandest  scientific  problems  that  remain  unsolved.  It 
seems  more  than  probable  that  it  is  to  the  mysteries 
and  lessons  of  life  that  the  chemist,  the  physicist,  the 
engineer,  must  turn  in  seeking  the  key  that  shall  un 
lock  the  still  unrevealed  treasures  of  coming  centuries. 
These  constitute  nature's  challenge  to  the  engineer. 


